Anesthetics 01-22, 24 Flashcards

Question

A 38-year-old woman is undergoing a routine abdominoplasty at an outpatient surgery center under general anesthesia. Thirty minutes into the operation, the anesthesiologist reports high end-tidal CO2 production and tachycardia. Which of the following is the most appropriate first step in management? A) Administer dantrolene B) Discontinue volatile anesthetic agents C) Infusion of lipid emulsion D) Switch to total intravenous anesthesia E) Treatment of arrhythmia

Answer 1

The correct response is Option B. Malignant hyperthermia is an anesthetic crisis that is potentially fatal if not appropriately managed. The mechanism of malignant hyperthermia is an accelerated release of calcium from the sarcoplasmic reticulum. The increasing release of calcium surpasses uptake and leads to an inability to control the intracellular calcium level. The symptoms of malignant hyperthermia include unexplained high end-tidal CO2 levels, tachycardia, increasing body temperature, masseter muscle rigidity, and skeletal muscle rigidity. The first step in the management of malignant hyperthermia is discontinuing the volatile anesthesia. The subsequent steps in management include administering dantrolene, switching to IV anesthesia, and treatment of arrhythmia. Depolarizing muscle relaxants can cause malignant hyperthermia and these drugs should be immediately discontinued and not administered. Infusion of lipid emulsion is done for lidocaine toxicity.

Answer 2

The correct response is Option E. Several studies have shown that timing of antibiotic delivery does impact the rate of surgical site infection (SSI). Current recommendations suggest that, when indicated, antibiotics should be given between 1 and 2 hours before surgery. There are no data to support a reduction in SSI risk when antibiotics are given within 30 minutes of surgery. In the retrospective review by Bykowski et al, authors reported the SSI rates in patients undergoing elective soft-tissue surgery. Rates of SSI did not differ between patients who received preoperative antibiotics and those who did not (0.54% versus 0.26%, p less than 0.05). When a subgroup analysis was performed, SSI infection rates for patients who were active smokers, diabetics, and with procedure length greater than 60 minutes showed no difference with or without antibiotic administration. Traditionally, patients with rheumatoid arthritis are viewed to be at higher risk for infection following surgery. There are no data to suggest that there is a risk reduction with the use of preoperative and/or postoperative antibiotics. Also, methotrexate does not increase one’s SSI risk and is therefore not an indication for perioperative antibiotic therapy.

Answer 3

The correct response is Option D. The advantage of using this combination is that midazolam has excellent anxiolytic and amnestic effects, whereas fentanyl is an excellent short-acting analgesic. A recent multicenter, randomized study demonstrated that the combination of fentanyl and midazolam is superior to midazolam alone in decreasing the patient’s subjective report of pain and anxiety. The main drawback of fentanyl is respiratory depression; however, it does have a very short half-life. Midazolam, in contrast, has minimal effects on the respiratory system except in some older patients, in whom lower doses must be used. Continuous oxygen saturation monitoring and checking the patient's respiratory status and other vital signs every 5 minutes are important for patient safety. Medications are only administered in small doses at each 5-minute interval (no more than 50 mg of fentanyl and 2 mg of midazolam at a time). This helps achieve a steady-state effect. Both of these medications have antagonists that are able to reverse their effects. Flumazenil and naloxone, the antagonists of midazolam and fentanyl, respectively, should be readily available in the operating room. The surgeon should be familiar with their dosage and administration. Ketamine would not resolve anxiety in this patient. Use of propofol in combination with an opiate and benzodiazepine can be used for conscious sedation; however, the disadvantage of this combination is the higher risk of respiratory depression and the lack of a reversing agent for propofol. Because a deeper level of sedation can be maintained, this technique is preferable for selected patients who are very anxious. A recently published series of abdominoplasty with sedation using propofol used monitored anesthesia care by an anesthesiologist or nurse anesthetist. Propofol and benzodiazepines have no significant analgesic effect.

Answer 4

The correct response is Option C. This patient is suffering from a bleeding disorder called von Willebrand disease (VWD), which occurs when the von Willebrand factor (VWF) is deficient or qualitatively abnormal. Von Willebrand factor (VWF) works by mediating the adherence of platelets to one another and to sites of vascular damage. It also binds to Factor VIII, keeping it inactive while in circulation since Factor VIII rapidly degrades when not bound to VWF. VWD is the most common of the inherited bleeding disorders, with an estimated prevalence in the general population of 1 percent by laboratory testing. Patients will often present with signs of easy bruising, extensive bleeding after dental work, heavy or long menstrual periods, and prolonged nose bleeds. Patients with a history of abnormal bleeding should always be properly worked up prior to surgery. There has been an extensive discussion over the years about the treatment of patients suffering from von Willebrand’s disease and rhinoplasty procedure. The recommended treatment of patients suffering from VWD undergoing rhinoplasty procedure is 0.3 ?g/kg of 1-deamino-8-D-arginine-vasopressin (Desmopressin). Desmopressin is an analogue of vasopressin that exerts a substantial hemostatic effect, by inducing the release of von Willebrand factor from its storage sites in endothelial cells. Patients with the mild form of VWD have lower than normal levels of VWF, and the release of the additional proteins from the endothelial cells aids with clotting. Factor V Leiden is a mutated form of human Factor V, which condition that result in a hypercoagulable state. Due to this mutation, Protein C, an anticoagulant protein which normally inhibits the pro-clotting activity of factor V, is not able to bind normally to Factor V, leading to a hypercoagulable state. Desmopressin does not have a direct interaction on this molecule. Thrombin is an enzyme that converts fibrinogen to fibrin, and a reaction that leads to the formation of a fibrin clot. There are several thrombin products commercially available. Hemophilia is a condition that is deficient in Factor VII. Recombinant activated factor VII. Aspirin irreversibly blocks the formation of thromboxane A2 in platelets, producing an inhibitory effect on platelet aggregation.

Answer 5

The correct response is Option A. The pH is low, indicating an acidosis, while the bicarbonate is high, indicating that a respiratory acidosis with metabolic compensation is present. The pH is low so the primary problem is an acidosis and is likely to be respiratory in nature. The PaCO2 is very high and indicates a respiratory acidosis is present. The very high PaCO2 level seen here is typical of a person with respiratory disease that results in retention of CO2, (ie, the primary clinical problem is respiratory failure due to chronic obstructive pulmonary disease).The most likely cause for this acid-base abnormality is an acute exacerbation of chronic obstructive pulmonary disease.

Answer 6

The correct response is Option A. The 2016 Surviving Sepsis Campaign guidelines strongly recommend that administration of intravenous antibiotics be initiated as soon as possible after recognition and within 1 hour for both sepsis and septic shock. In the presence of sepsis or septic shock, increasing delays in administration of appropriate antibiotics are associated with increasing mortality and detrimental effects on secondary endpoints, such as length of hospital stay, acute kidney injury, acute lung injury, and the Sepsis-Related Organ Assessment score. Although data suggest that optimal outcomes are achieved by the earliest possible administration of appropriate antibiotics following recognition of sepsis, 1 hour was recommended as a reasonable minimal target, considering multiple patient and organizational factors that may cause delay.

Answer 7

The correct response is Option E. Epinephrine is the initial drug of choice in the acute management of this patient with pulseless electrical activity (PEA). Desirable effects of epinephrine in the treatment of cardiac arrest include vasoconstriction (alpha-1 adrenergic) and increase in cardiac output (beta-1 adrenergic). According to current Advanced Cardiac Life Support guidelines, epinephrine should be administered to a patient in cardiac arrest as soon as the electrocardiographic diagnosis of either PEA or asystole is made. The intravenous dose is 1 mg every 3 to 5 minutes, always followed by a 20 mL normal saline flush. Cardiopulmonary resuscitation should not be halted for drug administration. The drug can also be administered via intraosseous access or through the endotracheal tube. The other drugs listed are not indicated in the initial treatment of PEA.

Answer 8

The correct response is Option A. Malignant hyperthermia is an autosomal dominant trait, thus, based on Mendelian Genetics, if one parent has a confirmed diagnosis, their biological children will have a 50% chance of inheritance of the affected gene. Malignant hyperthermia is a potentially life-threatening condition. Individuals with this inherited myopathy present with a hypermetabolic reaction to potent volatile anesthetic gases, such as halothane, enflurane, isoflurane, sevoflurane, and desflurane. Individuals are also susceptible to the depolarizing muscle relaxant succinylcholine. The preoperative workup for an individual with suspected malignant hyperthermia is the Caffeine-Halothane Contracture Test. In this test, a piece of skeletal muscle is excised, and its contractile properties are determined when exposed to the ryanodine receptor agonist halothane and/or caffeine. Abnormal contractile activity is indicative of susceptibility. Based on basic Mendelian Genetics, the risk of inheritance is 50%. Given this pattern of inheritance, x-linked, autosomal recessive and mitochondrial inheritance are incorrect answers.

Answer 9

The correct response is Option B. The patient is showing signs of symptomatic progressive intracranial pressure following head trauma. Hypertonic infusion therapy can be used in this scenario to decrease intracranial pressure and curtail progressive cerebral edema. Hypertonic (3%) saline fits into conventional algorithms for treatment of symptomatic acute intracranial hypertension along with hyperventilation, mannitol, diuretics, and surgical decompression. Hypertonic solutions have been shown to decrease intracranial pressure with greater efficiency than mannitol in early stages of trauma for patients with evolving brain injury. Ringer’s lactate and physiologic (0.9%) saline solution would not prevent or counteract progressive cerebral edema following head trauma. Hypotonic solutions (such as dextrose 5% in water and 0.45% saline solutions) are broadly contraindicated in patients who suffer severe traumatic brain injury, because they may lower serum osmolarity and exacerbate cerebral edema.

Answer 10

The correct response is Option E. Acute blood loss and the need for autologous blood transfusions are common in infants undergoing craniofacial procedures. Techniques to limit blood loss and transfusions have been studied extensively in craniosynostosis surgery. Tranexamic acid (TXA) is a synthetic analog of the amino acid lysine, which inhibits the conversion of plasminogen to plasmin when intravenously administered. TXA inhibits the proteolytic action of plasmin, thus inhibiting fibrinolysis. It has been shown in multiple studies to reduce both intraoperative and postoperative blood loss. Aprotinin is a small protein bovine pancreatic trypsin inhibitor with anti-thrombolytic potential. It was taken off the market in the United States in 2007 as its use was associated with increased complications and death. It has since been reapproved in Canada and Europe but remains banned in the United States. Protamine is a drug used to reduce the effects of heparin toxicity and of no benefit in this clinical scenario. Erythropoietin is a recombinant glycoprotein cytokine that stimulates red cell production. When given preoperatively, it has been shown to reduce the need for blood transfusion (not necessarily acute blood loss) in craniosynostosis surgery. Fibrinogen is not administered intravenously. Fibrin glue does reduce blood loss in craniosynostosis procedures, but it is administered topically, not intravenously.

Answer 11

The correct response is Option D. Indirect calorimetry measurements, or a metabolic cart, are used to help calculate the resting energy expenditure (REE) and respiratory quotient (RQ) as a means to help determine the caloric needs of a patient as well as optimize the patient’s nutrition. Indirect calorimetry measures the amount of oxygen consumed (VO2) and the amount of carbon dioxide produced (VCO2) by the patient. REE is calculated by the Weir equation [REE = (3.94 x VO2) + (1.1 x VCO2)] while the RQ is calculated as VCO2 / VO2. The calculated values of the respiratory quotient are reflections of what fuels are being oxidized by the patient with typical values as follows: Optimal values of RQ for nutrition assessment are between 0.8 and 0.9, representing a balance between lipid and glucose oxidation. Values below 0.8 suggest underfeeding, while values greater than 1.0 suggest overfeeding. A value of 1.3 in this patient suggests significant overfeeding and lipogenesis and the enteral nutrition should be adjusted based on the current energy expenditure obtained from indirect calorimetry. Ketosis is not measured by RQ.

Answer 12

The correct response is Option B. The direct anticoagulation agent rivaroxaban (Xarelto) is a direct anticoagulant, which acts within the clotting cascade by blocking Factor Xa, which, along with Factor Va, helps convert prothrombin to thrombin. This step in the cascade is where the intrinsic and extrinsic pathways intersect and the common pathway that leads to fibrinogen being cleaved to fibrin and stabilized by factor XIIIa as a cross-linked clot. Aspirin is a drug that interferes with platelet function. Coumadin affects the vitamin K dependent factors II (prothombin), VII, IX and X. Heparin prevents clot propagation by blocking thrombin-mediated activation of fibrinogen to fibrin. The primary benefits of the direct anticoagulation agents over coumadin include no need for monitoring and equivalence in efficacy across many clinical situations. It is excreted by the kidney, so dosages must be altered or the drug avoided in renal failure. A U.S. Food & Drug Administration–approved reversal agent, recombinant coagulation factor Xa (Andexxa), is now available on the market for life-threatening or uncontrolled bleeding in patients using direct anticoagulants affecting factor Xa, like rivaroxaban. Prior to this, administration of fresh frozen plasma (FFP) was the antidote of choice.

Answer 13

The correct response is Option D. Virchow recognized a triad of factors that predispose to intravascular thrombosis. These are stasis in blood flow, endothelial (intimal) damage, and intrinsic hypercoagulability. One recent review identifies a personal history of prior thrombotic event as perhaps the single greatest risk factor of a hypercoagulable state. Other known hypercoagulable disorders that can be identified by specific blood test include Factor V Leiden mutation, prothrombin gene (20210A) mutation, protein C deficiency, protein S deficiency, antithrombin III (AT3) deficiency, lupus anticoagulant, anticardiolipin antibodies, and anti-beta-2 glycoprotein 1 antibodies. These appear to increase the risk of microsurgical thrombotic complications as well. However, the severity of the increased risk for each remains to be fully elucidated. Another published series of 41 patients showed an 80% free flap success rate in patients with identified hypercoagulable states. Therefore, a thorough preoperative evaluation of patients for microvascular procedures may help to identify those at increased risk for thrombotic complications, guiding patient selection and perioperative anticoagulation therapy. The Caprini Risk Assessment Model (RAM) is used to assess venous thromboembolism (VTE) risk, and its use has been validated in plastic and reconstructive surgery patients. The Caprini RAM score for the patient in this question is 5 (2 risk factor points for major surgery over 45 minutes, 2 points for presence of malignancy, and 1 point for ages 41 to 60). According to the recommendations of the American Society of Plastic Surgeons VTE Task Force Report, one should consider postoperative chemoprophylaxis for VTE for this patient who is at intermediate risk. However, data are lacking, which would support the use of the Caprini Risk Assessment Model as a tool to stratify risk of microvascular thrombotic complications. This examination contains test materials that are owned and copyrighted by the American Society of Plastic Surgeons. Any reproduction of these materials or any part of them, through any means, including but not limited to, copying or printing electronic files, reconstruction through memorization or dictation, and/or dissemination of these materials or any part of them is strictly prohibited. Keep printed materials in a secure location when you are not reviewing them and discard them in a secure manner, such as shredding, when you have completed the examination. BRCA-2 genetic mutation is a heritable condition that significantly increases lifetime risk for breast and ovarian cancer. However, it has not been shown to play any role in risk for thrombotic events. Similarly, sickle cell trait (heterozygous carrier of the sickle cell mutation in the hemoglobin-beta gene) has not been shown to increase risk for microsurgical thrombotic complications. While chest wall irradiation might negatively impact the recipient chest wall vessels for deep inferior epigastric perforator (DIEP) flaps, the impact of radiation following a lumpectomy is very unlikely to be as significant as that of a prior personal thrombotic event.

Answer 14

The correct response is Option A. Traumatic placental injury can cause maternal-fetal hemorrhage in 10 to 30% of pregnant trauma patients. The majority of these are subclinical, without measurable effects to the fetus. However, as little as 0.001 milliliter of Rh-positive fetal blood can cause alloimmunization of an Rh-negative mother. Therefore, determination of Rh status is mandatory for all pregnant trauma patients and all Rh-negative of these should be given anti-D immune globulin (IgG). A single dose administered within 72 hours from injury may provide protection against sensitization in up to 90% of the cases. Higher doses may be necessary if it is determined that transplacental hemorrhage was in excess of 30 milliliters. Simply discharging the patient for a future obstetric follow up is not acceptable. At least 4 hours of electronic fetal monitoring should be provided to all pregnant trauma patients with \>= 23 weeks gestation. Internal electronic fetal heart rate monitoring (with an electrode in the scalp) is not indicated at this time. Instead, external monitoring could be done using a dedicated Doppler ultrasound device. MRI of the abdomen/pelvis and diagnostic peritoneal lavage are not indicated in the scenario described. Radiographic imaging generally indicated for trauma evaluation, including abdominal computed tomography, should not be deferred or delayed due to concerns of fetal exposure to radiation. Ultrasonography (FAST) should be part of the secondary survey in all pregnant trauma patients.

Answer 15

The correct response is Option E. Systematic review drawing from 30 studies and more than 14,000 patients undergoing minor cutaneous surgery firmly supports continuation of aspirin therapy in all minor cutaneous surgery, as patients on aspirin monotherapy are at no greater risk of hemorrhagic complications than those on no agents. While a case-by-case risk profiling in all patients on aspirin therapy is prudent, the preponderance of evidence favors meticulous hemostasis over aspirin cessation in prevention of bleeding complications in minor cutaneous surgery. There is no reported association between aspirin utilization and increased risk of wound dehiscence, wound infection, or cosmetic outcome.

Answer 16

The correct response is Option B. Enhanced recovery after surgery (ERAS) protocols are multimodal, multidisciplinary perioperative care pathways designed to achieve rapid recovery after surgery. These pathways include consensus recommendation for postoperative analgesia. In addition, improved postoperative pain control can be obtained with emphasis on the use of procedure-specific pain management. Some procedures have a higher propensity for persistent postoperative pain which generally are neuropathic in origin, ie: mastectomy, thoracotomy, hernia repair, abdominal wall surgeries. The primary goal of an optimal pain therapy is to provide “dynamic” pain relief (pain relief during movement) that would allow early ambulation while reducing opioid consumption. The ideal multimodal analgesic technique would include a local/regional analgesic (wound infiltration or peripheral nerve block) as the principal component because they provide excellent dynamic pain relief. Liposomal bupivacaine (Exparel) allows delivery of bupivacaine for 96 hours with a single local administration. There can be significant pain relief with the combination of wound infiltration with liposomal bupivacaine acetaminophen and NSAIDs or COX2 inhibitors as multimodal analgesic regimens. Epidural analgesia, dexamethasone, lidocaine and ketamine infusions all have demonstrated postoperative pain relief and reduction in opioid requirements to varying degrees. But local/regional analgesia (wound infiltration) should be used as the first-line analgesic therapy, which should be combined with acetaminophen, NSAIDs or COX1 inhibitors.

Answer 17

The correct response is Option D. Brain death is a criterion for nonliving organ donation. Absence of all brain stem reflexes needs to be present for brain death to occur. Absence of corneal reflex demonstrates an absence of brain stem reflexes. Presence of pupillary reflex and nystagmus during caloric test demonstrates a positive finding and presence of brain stem reflex. Mild cough or gag during tracheal manipulation demonstrates presence of brain stem reflex. Any respiratory rate during apnea test is seen as a sign of brain stem function. Evaluation of deep tendon reflexes is not part of assessing brain death.

Answer 18

The correct response is Option E. Postoperative nausea and vomiting remains a significant problem after cosmetic and reconstructive plastic surgery. Reported studies on the condition list incidences as high as 56%, whereas a meta-analysis found that the overall incidence was 28.3%. For many plastic surgery procedures, general inhalational anesthesia and narcotic pain control are required and may predispose patients to postoperative nausea and vomiting (PONV).The effects can be disastrous including hematoma, incisional dehiscence, respiratory compromise, pain, longer hospital stay, slower recuperation, and patient dissatisfaction. A number of risk factors have been associated with a positive overall incidence of PONV. Patient-specific risk factors for PONV in adults include female sex, a history of PONV, non-smoking status, young age, general versus regional anesthesia, postoperative opioids, and type of surgery. Other factors have been disproven including placement of a nasogastric tube, peri-operative fasting, obesity, and supplemental oxygen.

Answer 19

The correct response is Option E. Pregabalin (Lyrica) has been shown to decrease narcotic needs after breast surgery. It is a gamma-aminobutyric acid (GABA) analogue and decreases GABA in the brain and acts primarily as an anticonvulsant. It is more potent than gabapentin as an analgesic. Compression garments would be useful for post-mastectomy lymphedema but would not decrease narcotic needs. Hypnosis might decrease narcotic use slightly, but the effects are negligible. Oxycodone is a narcotic which does not decrease narcotic needs. The use of ondansetron (Zofran) has not been shown to reduce post-operative narcotic requirements.

Answer 20

The correct response is Option E. The primary mechanism of action for the increased bleeding time associated with the use of ketorolac is the inhibition of thromboxane A2. Ketorolac is a non-steroidal anti-inflammatory drug (NSAID). Most NSAIDs inhibit the activity of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2), and thereby the synthesis of thromboxane A2. This produces a systemic bleeding tendency by impairing thromboxane-dependent platelet aggregation and consequently prolonging the bleeding time. It is thought that inhibition of COX-2 leads to the anti-inflammatory, analgesic, and antipyretic effects through the inhibition of formation of prostaglandins and prostacyclin. Inhibition of lipoxygenase and nitric oxide are not the primary mechanisms associated with NSAID-related platelet inhibition.

Answer 21

The correct response is Option C. The patient shows all the signs of tension pneumothorax, and although the precise etiology is unclear, the patient requires decompression. Intubation will not help relieve the tension and pressure, with decreased venous return jeopardizing hemodynamic stability. Immediate chest x-ray is inappropriate because of the time required. Opening the chest incision is not a good option because it requires surgical equipment, general anesthesia, and cannot be completed in a timely fashion. Needle decompression at the second intercostal is the standard of care to decompress a tension pneumothorax. After oxygen saturation and hemodynamics are stabilized, definitive treatment of pneumothorax can be pursued. This would include placement of chest tube to low suction and serial chest x-ray to monitor the progress of the lung inflation. Arterial blood gas will not help make the diagnosis and potentially will delay the appropriate intervention.

Answer 22

The correct response is Option C. It is recommended that follow-up retesting be done at 6 weeks, 3 months, and 6 months in known HCV exposure cases. Tests at 1 or 3 weeks would possibly lead to false negative results. There is no advantage in waiting beyond 6 weeks.

Answer 23

The correct response is Option B. Postoperative delirium is an acute brain dysfunction that is characterized by changes in levels of consciousness, inattention, and disorganized thinking. There are two types of delirium. Delirium can manifest with hyperactive signs (agitation, restlessness), or hypoactive signs (lethargy, inattentiveness). It is very common in hospitalized patients, with 60 to 80% of mechanically ventilated patients and 20 to 50% of patients with a lower severity of illness developing delirium at some point during their hospitalization. For patients at risk of postoperative delirium, benzodiazepines and antihistamines should be avoided, as these medications could exacerbate the symptoms.

Answer 24

The correct response is Option E. This patient has acute kidney injury (AKI) after a surgical procedure. International practice guidelines recommend insulin therapy for targeted glucose control in critically ill patients. Although the Kidney Disease – Improving Global Outcomes (KDIGO) task force recommended a plasma glucose target of 110 to 149 mg/dL, the latest recommendation by the Surviving Sepsis Campaign is for an upper blood glucose level not higher than 180 mg/dL. Other recommendations for prevention and treatment of AKI by the 2012 KDIGO Clinical Practice Guideline included: Isotonic crystalloids rather than colloids (albumin or starches) as initial management for expansion of intravascular volume in patients at risk for or with AKI; Avoding restriction of protein intake with the aim of preventing or delaying initiation of renal replacement therapy (RRT); Administration of 0.8 to 1.0 g/kg/d of protein in non-catabolic AKI patients without need for dialysis; 1.0 to 1.5 g/kg/d in patients with AKI on RRT; and up to a maximum of 1.7 g/kg/d in patients on continuous renal replacement therapy (CRRT) and in hypercatabolic patients; Providing nutrition preferentially via the enteral route in patients with AKI; Not using diuretics to prevent AKI; Not using diuretics to treat AKI, except in the management of volume overload; Not using low-dose dopamine to prevent or treat AKI

Answer 25

The correct response is Option C. Obtaining a serum lactate level is the most appropriate next step for the diagnosis of septic shock in this scenario. Patients with septic shock can be clinically identified by having both of two criteria: Vasopressor requirement to maintain a mean arterial pressure of 65 mmHg or greater and Serum lactate level greater than 2 mmol/L (\>18 mg/dL) in the absence of hypovolemia. In 1991, a consensus task force developed initial definitions that focused on the prevailing view at the time that sepsis resulted from a host’s systemic inflammatory response syndrome (SIRS) to infection. SIRS was defined by the presence of two or more of four criteria, including body temperature, heart rate, respiratory rate, and white blood cell count. Despite their known limitations, these definitions remained mainly unchanged for almost three decades. In 2016, the Society of Critical Care Medicine and the European Society of Intensive Care Medicine sponsored a task force to review the definition of sepsis and its management guidelines (Sepsis-3). Sepsis is now defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. This organ dysfunction can be represented by an increase in the Sequential [Sepsis-related] Organ Failure Assessment (SOFA) score of two points or more. Another measure called quick SOFA (qSOFA), although less robust, may be more practical for providers diagnosing sepsis in the non-ICU setting. qSOFA incorporates altered mentation (GCS \<15), systolic blood pressure of 100 mmHg or less, and respiratory rate of 22/min or greater. Septic shock is a subset of sepsis with profound circulatory and cellular/metabolic dysfunction, associated with a higher risk of hospital mortality than with sepsis alone (40% versus 10%, respectively). The term "severe sepsis," previously defined as sepsis complicated by organ dysfunction, has been incorporated into the current definition of sepsis and abandoned.

Answer 26

The correct response is Option D. This patient is experiencing nephrotoxicity and chronic kidney disease (CKD) from tacrolimus. Calcineurin inhibitor nephrotoxicity is a well-known phenomenon posttransplantation, and close monitoring of kidney function is essential. There are multiple described pathways of kidney damage secondary to calcineurin inhibitors including irreversible damage to all compartments of the kidney (glomeruli, arterioles, and tubule-interstitium). Krezdorn et al. evaluated 99 recipients of facial or extremity transplantation and concluded that kidney dysfunction represents a major complication posttransplantation in vascularized composite allografts and recommends pretransplant, peritransplant, and posttransplant strategies to reduce kidney damage. These include identifying patients at risk for CKD. Pretransplantation recommendations include treating existing renal conditions, avoiding hypotension and hypertension, limiting nephrotoxic drugs, limiting intravenous contrast, and avoiding hypovolemia. Peritransplantation recommendations include minimizing use of nephrotoxic agents, avoiding hypovolemia, and limiting ischemia time. Postoperative recommendations include minimizing tacrolimus exposure including reduction of trough levels, treating hypertension, treating hyperglycemia, treating dyslipidemia avoiding intravenous contrast, and limiting potentially nephrotoxic drugs such as nonsteroidal anti-inflammatory drugs. Therefore, in this patient, tacrolimus troughs should be reduced. Initiation of oral corticosteroids is not appropriate. The patient should remain on antihypertensive and dyslipidemia drugs.

Answer 27

The correct response is Option A. Minors are neither eligible for nor able to receive organ donation without the consent of a parent or guardian. Creutzfeldt-Jakob disease or any other prion disease is a contraindication for organ donation of any kind. Metastatic cancer is a contraindication for organ donation. HIV status is no longer a contraindication to donate or receive an organ, provided the donor and recipient are both HIV positive.

Answer 28

The correct response is Option B. According to current Advanced Cardiac Life Support (ACLS) guidelines, CPR should be resumed immediately after shock delivery, without pausing for a rhythm or pulse check. It should begin with chest compressions and continue for 2 minutes, after which the rhythm should be checked and the cycle (shock/CPR 2 min/check) repeated if there is no return of spontaneous circulation (ROSC). Increasing emphasis has been placed on the importance of continuous “high-quality” chest compression (5 cm sternal depression, 100 to 120/min), to maximize tissue perfusion and probability of ROSC. A 30:2 compression:ventilation rate is recommended in the absence of an endotracheal or supraglottic airway. Otherwise, 10 breaths per minute should be delivered with continuous chest compressions. There are no studies directly addressing the timing of advanced airway placement and outcome during resuscitation from cardiac arrest. Although insertion of an endotracheal tube during ongoing chest compressions is possible, in most instances intubation is associated with interruption of compressions for many seconds. Particularly, patients with witnessed cardiac arrest from ventricular fibrillation or pulseless ventricular tachycardia may benefit from a few uninterrupted cycles of CPR prior to placement of an advanced airway. Adenosine is not indicated in the treatment of adult cardiac arrest. Capnometry/capnography requires placement of an endotracheal tube.

Answer 29

The correct response is Option A. Malignant hyperthermia is an inherited myopathy that is autosomal dominant with variable penetrance. Anesthetic agents that trigger malignant hyperthermia include halothane, enflurane, isoflurane, desflurane, sevoflurane, and succinylcholine. These agents trigger an earlier calcium release into the skeletal muscle, resulting in an abnormal buildup of calcium in the myoplasm. This flood of calcium causes the muscle to remain in a contracted state, producing high levels of lactic acid, carbon dioxide, phosphate, and heat. The resulting physiologic changes are metabolic acidosis, hypercapnia, hyperphosphatemia, and fever in a patient experiencing malignant hyperthermia. The treatment of malignant hyperthermia is discontinuation of volatile agents and succinylcholine, dantrolene, treatment of hyperkalemia and metabolic acidosis, and transfer to an acute care hospital.

Answer 30

The correct response is Option D. The ASPS recently published the first consensus statement/guidelines for antibiotic prophylaxis in plastic surgery which is based on comprehensive systematic review of the available evidence. Systemic antibiotic prophylaxis is recommended for clean-contaminated, contaminated, or dirty plastic surgery of the head and neck, orthognathic/mandibular, septoplasty/rhinoplasty, hand and upper limb, and skin. Antibiotic prophylaxis is also recommended to reduce surgical-site infection for clean plastic surgery of the breast. Antibiotic prophylaxis is not recommended to reduce surgical-site infection in clean surgical cases of the head and neck, orthognathic/mandibular area, hand and upper limb, skin, and abdominoplasty. With the exception of cosmetic breast surgery, clean operations have not been shown to benefit from routine antibiotic prophylaxis. Clean-contaminated and contaminated plastic surgical procedures do benefit from the use of antibiotic prophylaxis. The duration of antibiotic use should generally be limited to a single preoperative dose because studies have generally showed no benefit for longer term antibiotic prophylaxis. As far as choosing the antibiotic, it should have activity against the most frequently encountered microorganisms in postoperative surgical-site infections. Cefazolin as a single dose preoperatively is the most commonly recommended agent and would be considered appropriate in most cases. In the event of allergy or intolerance, clindamycin or vancomycin may be appropriate alternatives.

Answer 31

The correct response is Option B. This patient is experiencing symptoms of lidocaine toxicity. Lidocaine toxicity occurs within a few minutes after injection but can occur up to 60 minutes after injection. The maximum dose of lidocaine without epinephrine is 4.5 mg/kg and with epinephrine is 7 mg/kg. Symptoms of lidocaine toxicity can range from central nervous system (CNS) excitement (circumoral/tongue numbness, metallic taste, light-headedness, dizziness, visual and auditory disturbances, disorientation, drowsiness), and at higher doses CNS depression (muscle twitching, convulsions, unconsciousness, coma, respiratory depression and arrest, cardiovascular depression and collapse). Cardiovascular manifestations include chest pain, shortness of breath, palpitations, hypotension, and syncope. Of the options presented, fat emulsion (Intralipid) is the treatment of choice. Flumazenil is the treatment for benzodiazepine overdose, naloxone is for opioid overdose, dantrolene is for malignant hyperthermia, and propofol is used for induction and maintenance of general anesthesia.

Answer 32

The correct response is Option C. Superficial incisional surgical-site infection is defined by the following criteria: Date of event for infection occurs within 30 days of a procedure AND involves only skin and subcutaneous tissue of the incision AND the patient has at least one of the following: A. purulent drainage at incision site B. positive cultures from the incisions or underlying tissue C. superficial incision that is deliberately opened by a surgeon or other designee with the following signs or symptoms: pain or tenderness; localized swelling; erythema; or heat D. diagnosis by the surgeon or attending physician designee

Answer 33

The correct response is Option E. Early administration of antibiotics (less than 3 hours after injury) has been shown to be the most important determinant of infection prevention after traumatic open fractures of the lower extremity; this is more influential than other factors including time to initial washout, seniority of surgeon involved, as well as severity of the extremity trauma. Guidelines differ by institution but at least a cephalosporin is advocated with consideration given to additional gram-negative plus or minus anaerobic coverage in grossly contaminated wounds. In a large multi-institutional study of open fractures, Pollak et al, showed a significant decrease in infection rate with either early direct admission (\<2 hours) or transfer (\<11 hours) to a level I trauma center, though this was only true for the Gustilo Type III open tibial fracture subgroup and not all open fractures. The authors hypothesized that early transfer resulted in earlier administration of antibiotics, though this was not directly compared. While prompt debridement is important in obtaining wound control in traumatic lower-extremity open fractures, no clear advantage has been shown to debridement within 6 hours versus 24 hours, with the accepted standard that this can typically wait until daylight hours in the setting of timely prophylactic antibiotic administration. Intramedullary reaming has not been shown to decrease infection risk in open tibial fractures, although early skeletal reduction and stability will minimize ongoing soft tissue damage.

Answer 34

The correct response is Option B. Epinephrine is the first line of treatment for patients with anaphylaxis and should be administered intramuscularly (anterolateral thigh) as soon as the diagnosis is made. In a setting where an exact dose can be drawn up, the recommended dosage is 0.01 mg/kg (maximum dose of 0.5 mg), administered intramuscularly every 5 to 15 minutes as necessary to control symptoms. It can also be administered more frequently than every 5 minutes if needed. Greater emphasis has been placed on early administration of epinephrine in the management of anaphylaxis. The mean time to cardiac or respiratory arrest from medication-induced anaphylaxis in a hospital setting has been shown in one study to be only 5 minutes, with only 14% of patients receiving epinephrine prior to arrest. Besides intramuscular epinephrine, recommended immediate interventions for anaphylaxis include an assessment of airway, breathing, and circulation; intravenous access; supplemental oxygen; monitoring; and placing the patient in supine position. Depending on the initial response, other interventions include establishing an airway, rapid intravenous fluid infusion, intravenous epinephrine infusion, bronchodilators, steroids, H1/H2 antihistamines, and glucagon. Ketamine and midazolam (versed) are not indicated for the treatment of anaphylaxis. Diphenhydramine (Benadryl) and other antihistamine drugs are recommended as a second line of therapy for anaphylaxis. The same applies to systemic corticosteroids.

Answer 35

The correct response is Option C. Brain death is a permanent and irreversible state. There will be no return of cerebral or cortical function. Hypothermia is not required for brain death examination; it needs to be reversed for at least 4 hours (up to 24 hours) to establish brain death. Neuromuscular blockade must be reversed and patient must have normal peripheral muscle response to peripheral nerve stimulus in order to undergo brain death examination. Brain death examination includes elicitation of brain reflexes, which can be muted by neuromuscular blockade. Anoxic brain injury must be observed for at least 24 hours prior to beginning brain death examination. Cause or reason for brain death must be established prior to beginning brain death examination. Absence of deep tendon reflexes is not required to initiate the examination.

Answer 36

The correct response is Option C. Risk factors for postoperative nausea and vomiting fall into four categories: patient-related, anesthesia-related, surgery-related, and other factors. Patient-related predictors are: female sex, non-smoking status, history of postoperative nausea and vomiting/motion sickness, genetics, age of 50 years or younger, and obesity (BMI greater than 30 kg/m2). Anesthesia-related predictors are: postoperative opioids, inhalational anesthetics, and nitrous oxide. Surgery-related predictors are: surgery duration and surgery type. Other factors including high patient anxiety and postoperative pain.

Answer 37

The correct response is Option E. This patient developed a mild form of red man syndrome (RMS), caused by vancomycin administration. The most appropriate next step in management after discontinuing the antibiotic infusion is symptomatic treatment with an antihistamine drug (eg, intravenous or oral administration of diphenhydramine). The vancomycin infusion can be resumed after resolution of the rash and other symptoms, albeit at a slower rate. Vancomycin can cause a plethora of hypersensitivity reactions, ranging from localized skin reactions to anaphylactic shock. RMS is its most common form and consists of an erythematous rash that involves the face, neck, and upper torso, commonly associated with generalized discomfort and cutaneous pruritus or burning. Patients can experience headache, chills, fever, perioral paresthesia, and/or dizziness. Although rare, chest pain, diffuse muscle spasms, angioedema, and hypotension can also occur. RMS is associated with rapid intravenous infusion of vancomycin, occurring in less than 10% of patients with serious infections who receive 1 g infused over 1 hour. However, healthy patients may have a higher susceptibility. Contrary to true anaphylaxis, RMS is not thought to be mediated by vancomycin-specific antibodies, and can occur even with its first administration. Intramuscular injection of epinephrine is indicated for anaphylactic reactions. Morphine and other opioids have been shown to increase the rate of RMS in patients receiving vancomycin infusion, and, therefore, should be avoided. A vancomycin serum level at this time would unlikely provide any valuable information. RMS is not considered a patient-specific allergy, but rather an idiosyncratic reaction related to speed of drug infusion.

Answer 38

The correct response is Option E. Tension pneumothorax occurs when there is injury to the lung and air leakage into the pleural space that cannot escape. Each subsequent breath increases the volume of air in the pleural space and increases the intrapleural pressure. As pressure builds, structures of the chest are compressed, impairing ventilation and decreasing venous return. Tension pneumothorax is a clinical diagnosis. Features include tachypnea, dyspnea, jugular venous distention, decreased air entry, hyperresonance on the affected side, tracheal deviation to the opposite side, and hypotension. Treatment is immediate decompression of the pleural space with a long, large-bore needle followed by insertion of a chest tube. In this patient with a history of penetrating chest trauma, decreased breath sounds, and respiratory distress, tension pneumothorax is diagnosed. The trachea will be deviated to the contralateral side (left) and the patient will be hyperresonant to percussion on the right side. Cardiac murmur and hypertension are not features of tension pneumothorax. Urine output is irrelevant.

Answer 39

The correct response is Option C. In transplantation, rejection is categorized as hyperacute, accelerated, acute, and chronic. Hyperacute rejection is a humoral response mediated by antibodies that are already present in the host at the time of transplantation. It starts in the operating room, at the time blood flow to the transplanted organ is reestablished. Exposure to the graft tissue activates preexistent antibodies, which then activate the complement system, causing diffuse thrombosis in the graft's microcirculation and rapid ischemic failure, usually within the first few minutes to hours of graft reperfusion. Accelerated rejection is a cellular and humoral response that usually occurs between the second and fifth day after transplantation. Considered a variant of hyperacute rejection, it also results from recipient presensitization to donor tissue antigens, but without the formation of large numbers of preexistent antibodies. Instead, memory cells mediate a rapid immune response against the graft. Complement activation and intravascular thrombosis usually leads to graft loss. This patient is experiencing acute rejection, which is regulated by the activation of T-cells. It can occur at any time after the fifth postoperative day, although it is more common within the first 4 to 6 months. Clinical presentation depends on the transplanted organ, but is usually characterized by short-term organ dysfunction (eg, liver, kidney) or graft cutaneous/mucosal manifestations. A graft biopsy is usually necessary for diagnosis. The majority of acute rejections respond well to higher levels of immunosuppressive therapy, although recurrent events might be predictive of the development of chronic rejection. Chronic rejection is both an antibody- and cell-mediated immune response that causes indolent, progressive arterial sclerosis and fibrosis of the transplanted organ (eg, coronary atherosclerosis in hearts, bronchiolitis obliterans in lungs, vanishing bile duct syndrome in livers, etc). It usually clinically manifests itself several months to years after transplantation. Initial measurable organ dysfunction usually progresses to failure. Graft-versus-host disease is a cellular response caused by activation of the transplanted graft's immune cells by the recipient's tissues. It most commonly occurs several months after bone marrow or stem cell transplantation. Clinical manifestation varies, but usually involves tissues/organs of the recipient individual.

Answer 40

The correct response is Option A. Free water deficit is calculated by the formula: Water deficit = normal body water x (1-(Serum Na/140)). The calculated free water deficit is the amount of free water required to bring the sodium concentration back to normal. Free water deficits and the associated hypernatremia can occur with diabetes insipidus after closed head injuries and need to be corrected if present. Although this patient does have a closed head injury and is unresponsive, his serum sodium concentration is in the normal range, and no calculated free water replacement is necessary.

Answer 41

The correct response is Option C. Anesthetic blocks are routinely performed for office procedures. They are especially useful for facial procedures because of their reliable anatomy. Understanding the anatomy of each of the branches of the trigeminal nerve is important to successfully use this technique. The superior alveolar branch is a branch of the infraorbital nerve that controls sensation to the central and lateral incisor, the canine, and both bicuspid teeth. The first and second molars are not innervated by branches of the infraorbital nerve. The contralateral central incisor is not innervated by the contralateral infraorbital nerve.

Answer 42

The correct response is Option E. For patients in lithotomy position, the use of leg holders that incorporate heel support may prevent compression injury to the peroneal nerve. Contrarily, leg holders without heel support or the use of wraps to maintain the leg on leg rests may increase the risk of compression injuries to this nerve. For prevention of brachial plexus perioperative neuropathy in the supine patient, arm abduction should be limited to no greater than 90 degrees. In addition, dorsal extension of the arm (poorly padded or sagging arm boards) should be avoided. For prevention of ulnar perioperative neuropathy in the supine patient, care should be taken to decrease pressure on the post-condylar (ulnar) groove of the humerus. When the upper extremity is on an arm board, the forearm should be positioned in either supination or neutral positions. When tucked at side, the forearm should be in a neutral position. When in prone position, the patient's neck should be well stabilized in neutral, nonextended position. Although neck extension has not been reportedly associated with peripheral neuropathies, authors have reported cases of vertebral artery injury.

Answer 43

The correct response is Option C. Pregnancy alters normal physiology as well as anatomy. At 32 weeks' pregnancy, gravid uterus and fetus is anatomically at the costal margin and can be somewhat protective of bowel injury in a restrained passenger. A hematocrit of 31 to 35% is within normal range; however, the overall volume has increased dramatically and a loss of 1.2 to 1.5 L is well tolerated without symptoms. Another crucial anatomical difference is the gravid uterus and its ability to compress the vena cava while in the supine position. Thirty percent decreased cardiac output can occur from the uterus occluding venous return from the lower extremity. In order to avoid this, the uterus should be physically displaced to the patient's left side to allow return from the inferior vena cava. Should there be cervical spine precautions, the board can be rolled to the left 4 to 6 inches, thus alleviating pressure. In general, pregnant patients should be monitored on their left side. Maternal well-being is the most crucial for fetal well-being, as the number one cause of fetal death is maternal hypotension and maternal death. The second most common cause of fetal death is abruption of the placenta. Fetal monitoring is extremely important, especially after 20 to 24 weeks' gestation. However, in this case there is no evidence of cramping or tender abdomen. Advanced Trauma Life Support (ATLS) protocol dictates airway, breathing, and circulation are normal, and, in this case, her airway and breathing are normal. The most appropriate next step is reestablishing this patient's circulation, which is alleviating the initial possibility of decreased venous return. Should this not occur, then following the protocol for crystalloid resuscitation would be the most appropriate.

Answer 44

The correct response is Option B. The peripheral nerve block described is a transversus abdominis plane, or TAP, block. The lumbar (Petit) triangle, which is located at the lateral extent of the abdomen, is formed by the borders of the latissimus dorsi muscle posteriorly, the external oblique anteriorly, and the iliac crest inferiorly. Furthermore, the location can be estimated by the intersection of a horizontal line through the umbilicus and the vertical anterior axillary line. The intercostal nerves providing sensation to the anterior abdominal wall from T6 to L1 are located in the plane between the internal oblique and the transversus abdominis muscles. Long-acting local anesthetic infiltration in this plane is generally approached through the lumbar triangle. Multiple techniques have been described. These include visualized injection with the assistance of ultrasound guidance, catheter insertion under direct vision with surgical cutdown to the appropriate plane, and blind injection using a blunt needle, feeling for the two punctures of the external and internal obliques, respectively. Multiple studies have shown improved postoperative pain control in the abdominal donor site with this technique in breast reconstruction, and patients have demonstrated marked decreases in opioid consumption as well. The other options would be inappropriate for nerve block as the intercostal nerves are not found in those tissue planes.

Answer 45

The correct response is Option B. The physiological abnormalities that result from rhabdomyolysis are caused because of crush injury to the muscle. The crush injury causes pressure or stretching of the muscle and sarcolemmal membrane. As the sarcolemmal membrane is stretched, sodium, calcium (hypocalcemia), and water leak into the sarcoplasm, trapping extracellular fluid inside muscle cells. In addition to the influx of these elements into the cell, the cell releases potassium (hyperkalemia) and other toxic substances such as myoglobin, phosphate, and urate into the circulatory system (metabolic acidosis). The end result of these events is shock, hyperkalemia, hypocalcemia, metabolic acidosis, compartment syndrome, and acute renal failure. Acute renal failure results because of a combination of hypovolemia with subsequent renal vasoconstriction, metabolic acidosis and the influx of nephrotoxic substances such as myoglobin, urate, and phosphate.

Answer 46

The correct response is Option E. Neurogenic or central diabetes insipidus is often caused by head trauma resulting in a lack of vasopressin production. Vasopressin is released by the posterior pituitary gland but, unlike other pituitary hormones, is produced in the hypothalamus. Because of this unique relationship, traumatically induced neurogenic diabetes insipidus may occur due to damage to the hypothalamus, pituitary stalk, or posterior pituitary. Vasopressin, also known as antidiuretic hormone (ADH), plays a key role in fluid homeostasis by affecting water retention in the kidneys at the collecting ducts and distal convoluted tubule. Cortisol is a hormone secreted by the adrenal glands that plays a role in numerous functions including maintaining normal metabolism and regulation of fluid balance. Angiotensin and aldosterone are key hormones of the renin-angiotensin system that is involved in the regulation of plasma sodium concentration and arterial blood pressure. Renin (also known as angiotensinogenase) is an enzyme that converts angiotensinogen to angiotensin. Angiotensin is a peptide hormone that causes vasoconstriction. It is formed by the action of renin on the liver-derived precursor, angiotensinogen, followed by the action of angiotensin-converting enzyme (ACE) to convert angiotensin I to the active form angiotensin II. Aldosterone is a steroid hormone produced by the adrenal glands and released in response to increased angiotensin. It plays a central role in regulation of plasma sodium, extracellular potassium, and arterial blood pressure. Cortisol, renin, angiotensin, and aldosterone deficiencies are not created by neurogenic diabetes insipidus related to head trauma.

Answer 47

The correct response is Option E. Conscious sedation is a common anesthetic technique used routinely by plastic surgeons for cosmetic procedures. The patient described is healthy and of average size. The two drugs used in this study are the most commonly used agents for this scenario. The dose chosen is on the low end of normal for both drugs. Increasing the amount of intravenous fluids is the correct answer because in the Marcus et al paper, 20% of the patients who underwent a similar conscious sedation procedure experienced this scenario. One hundred percent of these patients responded appropriately to increased intravenous fluid. Administration of flumazenil to reverse midazolam toxicity is unnecessary as the patient is not experiencing midazolam toxicity. The dosage of midazolam is within the normal range. The patient is not demonstrating any additional signs or symptoms of narcotic (fentanyl) toxicity. The dose is on the low side of normal. Reversal of fentanyl is not indicated. The patient's systolic blood pressure is only mildly low with no other symptoms in an otherwise healthy adult woman. Vasopressors would only be indicated if a fluid challenge was unsuccessful.

Answer 48

The correct response is Option D. The Rapid Response Team (RRT) was conceptualized to intervene in the care of a greater number of hospitalized patients at an earlier stage of clinical deterioration. The goal of the RRT is to act acutely to prevent catastrophic adverse events. The RRT would typically be called for hypotension, rapid heart rate, respiratory distress, and altered consciousness. While the traditional code team would treat cardiac arrest, respiratory arrest, and airway obstruction, the RRT would assess and manage sepsis, pulmonary edema, arrhythmia and respiratory failure. Typically, hospital mortality in patients treated is 70 to 90% for the traditional code team, while it is 0 to 20% for the RRT.

Answer 49

The correct response is Option B. The transversus abdominis plane (TAP) block is a regional anesthetic that blocks sensory afferent nerve fibers that supply the anterior/lateral abdominal wall dermatomes of T6-L1. These sensory nerves travel below the internal oblique muscle in the plane above the transversus abdominis muscle. Traditionally, the technique is performed blindly by placing a needle through the triangle of Petit posteriorly until the needle reaches the TAP. Once the needle is in the appropriate plane, 20 mL of a long-acting local anesthetic, such as bupivacaine, is injected. More recent modifications include the use of ultrasound guidance to optimize precise placement and the use of diluted long-acting multivesicular liposomal bupivacaine (Exparel). Several studies have demonstrated the benefits of a TAP block during abdominal surgery. These benefits include decreased pain, opioid use, and nausea/vomiting, as well as faster return of bowel function. Complications include potential systemic toxicity due to dose of anesthetic delivered/inadvertent intravascular injection and intraperitoneal injection with possible injury to intraabdominal organs such as, the liver or spleen.

Answer 50

The correct response is Option B. This patient meets the diagnostic criteria for anaphylaxis, manifested by acute onset of generalized hives and swelling along with either respiratory compromise or hypotension. Intramuscular injection of epinephrine, 0.3 to 0.5 mg, preferably in the mid-outer thigh, is the initial treatment in adults. Other treatments include administration of supplemental oxygen and rapid normal saline infusion. Absorption of epinephrine after subcutaneous injection may be too slow to reverse anaphylaxis. Bolus injections of epinephrine should be avoided because of the risks of dosing errors and overdose. Epinephrine infusion can be considered for anaphylaxis that is refractory to intramuscular injections, but it is not a first-line choice. Subcutaneous or intradermal injection would result in delayed absorption.

Answer 51

The correct response is Option D. Wide-awake hand surgery has been successfully performed for a number of procedures including nerve decompression, excision of soft-tissue tumors, fracture repair, arthrodesis, tendon repair, and fasciectomy for Dupuytren disease. The wide-awake technique allows the surgeon to perform the procedure without general anesthetic or sedation and often without the use of a tourniquet to minimize tourniquet pain. In order to successfully use this technique, a bloodless field is paramount, and allowing the epinephrine to achieve maximal vasoconstrictive effect is essential. A prospective, randomized, triple-blind study was performed comparing the subcutaneous hemoglobin level at various times in patients after undergoing local anesthetic infiltration of lidocaine with epinephrine in one arm and plain lidocaine in the contralateral arm as the control. This study demonstrated that the lowest cutaneous hemoglobin level in the epinephrine group was obtained 25.9 minutes after injection. This is considerably longer than the 7 to 10 minutes often cited in the literature. The authors recommend waiting 25 minutes after injection if optimal visualization is desired.

Answer 52

The correct response is Option D. Asymptomatic ventricular premature beats (VPBs) and nonsustained ventricular tachycardia (NSVT) are not uncommon following myocardial infarction (MI), with reported incidences as high as 93% and 7%, respectively. These arrhythmias are thought to arise from transient abnormalities of cardiac automaticity or triggered activity in the region of ischemia or infarction. Routine suppression in the absence of hemodynamic compromise does not improve overall mortality, and because treatment may be associated with numerous potential adverse effects, antiarrhythmic medications are not recommended in this setting. Maintaining serum potassium concentration above 4.0 mEq/L and serum magnesium concentration above 2 mg/dL to normal ranges per general ACC/AHA guidelines followed by expectant management is the most reasonable option in this scenario. In stark contrast, ventricular fibrillation (VF) and other symptomatic sustained ventricular tachyarrhythmias are thought to be indicators, if not potentiators, of ongoing myocardial ischemia and sudden cardiac death following acute MI. Consequently, rapid identification and treatment of these arrhythmias using defibrillation with or without antiarrhythmic medications, according to ACLS protocols, can be lifesaving. When indicated, amiodarone would be the recommended antiarrhythmic in this setting because it has not been associated with increased mortality. Both flecainide and lidocaine have been associated with increased mortality in the post-MI period and are therefore not recommended in the scenario described. Intravenous administration of beta-adrenergic blockers has demonstrated numerous positive effects post MI including a reduced risk of VF. In the absence of other contraindications such as reactive airway disease and hypoperfusion, its ongoing administration in order to maintain a resting heart rate below 70 bpm is generally supported by the ACC/AHA guidelines for management of patients with STEMI. Hypokalemia during an acute MI is a risk factor for VF, while hypomagnesemia can interfere with correction of hypokalemia, which is why ACC/AHA guidelines generally recommend maintaining normal concentrations in patients with an acute MI.

Answer 53

The correct response is Option D. For surgical procedures not involving the airway, open oxygen sources such as masks or nasal cannulae are most likely to increase the risk of fire in the operating room, as they may allow for trapping or pooling of an oxidizer-enriched atmosphere (oxygen with or without nitrous oxide). The incidence of operating room fires in the United States is estimated to be around 600 cases per year. Fire requires the presence of three components: fuel, an oxidizer, and an ignition source. Common fuels in the operating room include alcohol-containing prepping agents, drapes and bandages, gowns and other personal protection equipment, petroleum jelly, etc. Ignition sources include electrocautery, lasers, fiberoptic light sources, and defibrillators. The two most common oxidizing agents in the operating room are oxygen and nitrous oxide. Most protocols for assessment of risk of fire in the operating room take into account the presence of an open oxygen source, surgical site or incision above the xiphoid, and an available ignition source (such as electrocautery, laser, fiberoptic light source, etc). For surgical procedures not involving the airway, closed-system oxygen sources using endotracheal/endobronchial tubes, tracheostomy cuffed tubes, or laryngeal masks convey less risk of fire, when compared with open oxygen sources.

Answer 54

The correct response is Option A. The transverse abdominis plane (TAP) block is a peripheral nerve block designed to anesthetize the nerves supplying the anterior abdominal wall (T6 to L1). Local anesthetic is injected between the internal oblique and the transverse abdominis muscles in the plane through which the sensory nerves pass. Use of this technique provides a suitable block to the multiple nerves supplying the abdominal wall with a single needle stick. The technique was first described in 2001 by Rafi using the anatomical landmarks of the inferior lumbar triangle (triangle of Petit): the anterior border of the latissimus dorsi muscle posteriorly, the posterior edge of the external oblique muscle anteriorly, and the superior edge of the iliac crest inferiorly. The effectiveness of this technique has been demonstrated in the general surgery and OB-GYN literature with recent studies also being performed specifically in the harvest of abdominal free flaps for breast reconstruction. In a recent meta-analysis of this technique, the TAP block decreased narcotic use, provided more effective pain relief, and decreased opioid-related side effects including sedation and postoperative nausea and vomiting. The teres major, teres minor, and long head of the triceps muscles form the borders of the triangular space through which the circumflex scapular artery can be found when harvesting the scapular flap. Hesselbach triangle is bounded by the lateral border of the rectus muscle (linea semilunaris), the inferior epigastric vessels, and the inguinal ligament and is the space through which direct inguinal hernias pass. The quadratus lumborum, internal oblique, and 12th rib are the anatomical landmarks of the superior lumbar triangle (Grynfeltt triangle) and a site of lumbar herniation.

Answer 55

The correct response is Option E. Acute hyperkalemia is an electrolyte derangement that can result from a variety of scenarios including supratherapeutic potassium replacement, rhabdomyolysis, hemolysis, tumor lysis syndrome, severe sepsis, acute renal failure, and Addison disease. Among the most serious manifestations are progressive neuromuscular paralysis and progressive volatility in cardiac conduction terminating in cardiac arrest. The spectrum of cardiac collapse is evident on ECG starting with peaked T waves, decreased P wave amplitude, and prolonged QRS wave duration, followed by progressive blending of QRS and T waves into a sinusoidal ventricular fibrillation, followed by asystole. Because cardiac arrest can occur at any point during ECG progression, hyperkalemia with ECG changes constitutes a medical emergency. Rapidly acting treatments aimed at sequestering or reducing serum potassium include administration of calcium, insulin with glucose, beta-2-adrenergeic agonists (e.g., albuterol, sodium bicarbonate), potassium wasting diuretics (e.g. furosemide), cation exchange resins (e.g., Kayexalate), and dialysis. Of the options listed, only insulin with glucose is an accepted rapidly acting treatment for hyperkalemia. It works primarily by driving via the activity of the Na-K-ATPase pump in skeletal muscle. The effect begins in 10 to 20 minutes, peaks at 30 to 60 minutes, and lasts for four to six hours. Insulin can be given alone if serum glucose is \> 250 mg/dL, and treatment can be repeated as needed. In all cases, serum glucose should be monitored to avoid acute hypoglycemia.

Answer 56

The correct response is Option A. Aprepitant 40 mg should be administered orally 1 to 3 hours before induction of anesthesia. Postoperative nausea and vomiting is a common complication after receiving general anesthesia. The overall incidence of this complication for all operations and patient populations is approximately 30% and increases to nearly 40% in patients treated at outpatient surgery centers. In patients who are at increased risk, the incidence of postoperative nausea and vomiting can be as high as 70 to 80%. Approximately 65% of all surgical procedures are now done on an outpatient basis and, if untreated, one third of these patients will have this complication. No antiemetic is universally effective in the prevention and treatment of postoperative nausea and vomiting. Each additional prophylactic antiemetic will decrease its incidence by approximately 25%. Aprepitant is a highly selective, brain-penetrant, neurokinin-1 receptor antagonist with a long half-life and clinical efficacy against opioid-induced vomiting. It is the first in its class to be approved for this indication. Neurokinin-1 receptor antagonists act by blocking the binding of substance P at the neurokinin-1 receptor in the brain stem emetic center and gastrointestinal tract. Because of its mechanism of action and long half-life, it is most effective when administered as prophylaxis before surgery in patients who are at high risk for postoperative nausea and vomiting. The remaining drugs all have short durations of action and are most effective when administered postoperatively. Ondansetron is a serotonin (5-HT3) receptor antagonist that exerts its effect on the chemoreceptor trigger zone and vagal afferents in the gastrointestinal tract. Droperidol blocks dopamine receptors and has an efficacy equivalent to that of ondansetron. Promethazine is a phenothiazine that acts primarily via central antidopaminergic mechanism. Metoclopramide blocks dopamine receptors in the central vomiting center and can block serotonin receptors at high doses.

Answer 57

The correct response is Option D. The seizure in this scenario is related to lidocaine toxicity. A seizure in this scenario can be related to head trauma, but the mechanism of injury is not likely to have caused an intracranial injury. Hypoxia can also cause a seizure but is unlikely with a functioning pulse oximeter showing good oxygen saturation and normal vital signs. Lidocaine toxicity is the most likely cause. The safe limit of lidocaine dosage is 7 mg/kg when given with epinephrine. This patient received 60 mL of 0.5% lidocaine, or 300 mg (0.5% solution contains 5 mg/cc). The safe limit for this patient is 133 mg (19 x 7). The first signs of lidocaine toxicity in an awake and conscious patient is tinnitus. Seizures and cardiac arrhythmias follow. Treatment is supportive with establishment of an airway and vascular access. Lipid emulsion is provided intravenously due to the lipophilic nature of the local anesthetic and therefore hastens elimination. Epinephrine toxicity causes tachyarrhythmias and hypertension. Lidocaine is an amide anesthetic. Administration of epinephrine would be appropriate if anaphylaxis from the preservative in the local anesthesia were suspected. This would present with hypotension and tachycardia. Propofol would stop the seizures, but is contraindicated due to its confounding effects on cardiac arrhythmias in the face of lidocaine toxicity. Lipid emulsion therapy will hasten the clearance of the excess of lidocaine, however, it is first most important to secure the airway and ventilate.

Answer 58

The correct response is Option B. The patient is undergoing a transversus abdominis plane (TAP) block. TAP blocks have become popular adjunctive pain control measures for a variety of abdominal surgeries. They can either be performed transcutaneously with ultrasound guidance or under direct visualization in the operating room prior to closure of the abdominal donor site in deep inferior epigastric artery perforator (DIEP) or transverse rectus abdominis musculocutaneous (TRAM) flap surgeries. The segmental innervation to be blocked in the TAP block is located between the internal oblique and transversus abdominis muscles. Either infiltration of liposomal bupivacaine or placement of epidural catheters in the TAP space has been described.

Answer 59

The correct response is Option B. This patient has sustained a cardiovascular collapse secondary to local anesthetic systemic toxicity (LAST). The maximum safe dose of lidocaine with epinephrine in this patient is 35 to 55 mg/kg. Lipid Rescue protocol recommends an initial intralipid 20% bolus of 1.5 mL/kg over 1 minute. This should be followed immediately with a continuous infusion at 0.25 mL/kg/min. A single bolus is typical, but should be repeated or the infusion increased if spontaneous circulation fails to return or blood pressure declines. Cardiovascular collapse from LAST differs from that secondary to myocardial ischemia. In LAST, raising the peripheral vascular resistance with vasopressors like vasopressin, can impair cardiac output and impede resuscitation. Epinephrine should be given in small doses (\<1 mcg/kg). Pharmacologic agents that reduce contractility (beta blockers {propranolol}, calcium channel blockers {verapamil}, or propofol) should be avoided when there is evidence of cardiovascular instability. Adenosine is not useful in the management of LAST patients. It is typically used to treat supraventricular tachycardia.

Answer 60

The correct response is Option E. No further preoperative cardiac testing is needed for this patient being considered for an elective, greater-than-low-risk procedure, without any evidence of active cardiac conditions or clinical risk factors, and with moderate functional capacity (metabolic equivalents, or METs, \>= 4). Assessment of left ventricular function at rest, whether by echocardiogram, radionuclide angiogram, or contrast ventriculography, has not been shown to be a consistent predictor of perioperative ischemic events. Cardiac stress testing, including by exercise or drug induced, is not indicated in this patient. In 2007, the American College of Cardiology and the American Heart Association published updated guidelines on perioperative cardiovascular evaluation and care for noncardiac surgery (NCS), suggesting a stepwise algorithmic approach to perioperative cardiac risk assessment: Is there need for emergency NCS? If yes, proceed with surgery. Are there active cardiac conditions (unstable coronary syndromes, decompensated heart failure, significant arrhythmias, severe valvular disease)? If yes, evaluate and treat per specific guidelines before considering NCS. Is the NCS considered low risk (e.g., superficial and ophthalmologic procedures)? If yes, proceed with low-risk NCS. Does the patient have good functional capacity (METs \>= 4) without symptoms? If yes, proceed with NCS. Is there need for emergency NCS? If yes, proceed with surgery. Three or more clinical risk factors undergoing vascular surgery: consider testing if it will change management One or two clinical risk factors undergoing vascular surgery or one or more clinical risk factors undergoing intermediate-risk surgery: either proceed with surgery with heart rate control (beta blockade) or consider noninvasive testing if it will change management Preoperative cardiac assessment should include an estimation of the patient’s functional capacity, based on his/her ability to perform a spectrum of common daily tasks. This has been shown to correlate well with maximum oxygen uptake by treadmill testing. Four METs is a common threshold used in many decision-making points in the perioperative cardiac evaluation.

Answer 61

The correct response is Option A. A patient who underwent placement of a drug-eluting stent 4 months ago should continue on aspirin and clopidogrel for at least 6 months, except in cases with high risk of bleeding (intracranial or spine surgery). The combination of aspirin and clopidogrel appears to reduce the rates of cardiovascular ischemic events. Patients with coronary stents have an 8 to 10% risk of developing major adverse cardiovascular events and stent thrombosis after elective noncardiac surgery, which exceeds the 1 to 5% risk of major adverse cardiovascular events in non-stented patients having noncardiac surgery.

Answer 62

The correct response is Option C. Immediate cardioversion is recommended for patients with atrial fibrillation (AF) or atrial flutter with rapid ventricular response associated with hemodynamic instability such as hypotension, ongoing myocardial ischemia, or decompensated heart failure. Both chemical and electrical cardioversion can be attempted according to established protocols until sinus rhythm is restored with a goal of optimizing hemodynamic parameters. If initial cardioversion is unsuccessful, repeated attempts at cardioversion may be made after adjusting the location of the electrodes, applying pressure over the electrodes, or following administration of an antiarrhythmic medication according to Advanced Cardiac Life Support (ACLS) algorithms. A trial of medical management for rate control is appropriate in the absence of hemodynamic instability. In general, beta blockers are the most common agents used for rate control, followed by nondihydropyridine calcium channel blockers such as diltiazem, as well as other agents such as digoxin and amiodarone. Patient comorbidities influence the choice of medical therapy to minimize risk of adverse events such as heart failure decompensation, exacerbation of chronic obstructive pulmonary disease, or acceleration of conduction in patients with preexcitation physiology. Appropriate anticoagulation management around the time of elective cardioversion is essential for reducing thromboembolic risk. When AF has clearly existed at \< 48 hours’ duration, it is common practice to perform cardioversion without transesophageal echocardiography (TEE) or antecedent anticoagulation. When AF has existed at \>48 hours’ duration or duration is unknown, then anticoagulation for ? 3 weeks before and continuing for ? 4 weeks after cardioversion is recommended unless otherwise contraindicated. In case of relative contraindications to anticoagulation, TEE can be performed to help guide relative risk assessment related to thromboembolism of preexisting cardiac thrombi arising in the setting of prolonged atrial dysfunction. Importantly, when emergent cardioversion is indicated because of hemodynamic instability, initiation of anticoagulation and TEE should not delay acute interventions to stabilize the patient's condition. AV nodal ablation with permanent ventricular pacing can be considered to improve rate control when other attempts at maintaining rate control through medical management are unsuccessful. This intervention is usually reserved for elderly patients, because it leads to pacemaker dependency. However, patients with symptoms refractory to medical therapy who are treated with AV nodal ablation and permanent pacemaker implantation have demonstrated an improvement in cardiac symptoms, quality of life, and health care utilization.

Answer 63

The correct response is Option D In surgical patients with von Willebrand disease (vWD) receiving desmopressin (DDAVP) for bleeding prophylaxis, total preoperative dose should be determined by preoperative measurement of activity levels of von Willebrand factor ristocetin cofactor (vWF:RCoF) and coagulation factor VIII. The other listed coagulation factors are not associated with isolated vWD. vWD is the most common congenital bleeding disorder, with estimated prevalence as high as 1.3%. It is caused by deficiency (types I and III) or dysfunction (type II) of von Willebrand factor (vWF), leading to impaired platelet adhesion and possibly lower levels of coagulation factor VIII. In its normal state, vWF is a plasma protein that mediates the initial adhesion of platelets at sites of vascular injury and also binds and stabilizes coagulation factor VIII in the circulation. Both vascular endothelial cells and platelets synthesize and store vWF. DDAVP is a synthetic derivative of ADH (vasopressin, antidiuretic hormone) that is used for treatment and prophylaxis of bleeding in patients with vWD. It promotes release of stored vWF from endothelial cells into the plasma, being particularly effective in patients with partial quantitative deficiency of vWF, or type I (about 75% of cases of vWD). Patients who do not appropriately respond to DDAVP administration should receive vWF concentrate. For bleeding prophylaxis for minor surgery, the preoperative goal should be to achieve vFW:RCoF and factor VIII activity levels of at least 30 IU/dL (preferably \>50 IU/dL). Such levels should be maintained for 1 to 5 days postoperatively. For prophylaxis for major surgery, preoperative activity levels should be at least 100 IU/dL and maintained above 50 IU/dL for at least 7 to 10 days. To decrease risk of perioperative thromboembolism, vWF:RCoF levels should not exceed 200 IU/dL and factor VIII activity should not exceed 250 IU/dL. Fluid restriction is advised for patients receiving DDAVP perioperatively, to avoid hyponatremia and seizures.

Answer 64

The correct response is Option C. This patient is presenting with anaphylaxis. The first and most crucial step in managing acute anaphylaxis is the administration of epinephrine. Anaphylaxis is a serious and life-threatening hypersensitivity reaction. Medications and insect stings are the most common triggers in adults, with beta-lactam antibiotic exposure among the most implicated medications. In this setting, anaphylaxis is diagnosed when two or more of the following are observed minutes to hours after exposure: Skin-mucosal tissue reactions (such as generalized urticaria, swollen lip, pruritus, and flushing) Respiratory compromise (such as dyspnea, wheeze, bronchospasm, stridor, and hypoxemia) Hypotension or associated findings (such as syncope, confusion, collapse, and incontinence) Persistent gastrointestinal reactions (such as crampy abdominal pain and vomiting) Intramuscular epinephrine can be repeated every 5 to 15 minutes as needed. If given promptly, most patients respond to one or two doses. Simultaneous with this treatment, an emergency team can be summoned. The patient should be placed in a recumbent position with legs elevated and supplemental oxygen administered. Volume resuscitation can be initiated to compensate for severe loss of intravascular volume that can accompany fluid shifts of untreated anaphylaxis and to support blood pressure not responsive to epinephrine. Bronchodilators, H1 and H2 antihistamines such as diphenhydramine and ranitidine, and glucocorticoids such as methylprednisolone are all reasonable but second-line treatments for acute anaphylaxis. Intubation should be performed immediately in the setting of progressive upper airway closure such as stridor and tongue edema, or if respiratory arrest is present. However, first-dose epinephrine administration should not be delayed for intubation. Epinephrine works rapidly to reduce airway edema that might otherwise prevent successful intubation, if not completely reverse the underlying etiology of cardiopulmonary collapse in anaphylaxis. While cardiovascular disease is a risk factor for poor outcome from anaphylaxis, it is not a contraindication for epinephrine administration. It is generally accepted that the risk of death or brain damage from prolonged or undertreated anaphylaxis outweighs the risk of appropriately administered epinephrine. If there is inadequate response to initial intramuscular epinephrine and volume resuscitation, then intravenous epinephrine can be introduced in an intensive care setting by slow infusion at 2 to 10 mcg per minute and titrated to effect.

Answer 65

The correct response is Option (sic) Hypotension is most likely to alter pulse oximetry values by reducing peripheral arterial blood flow. Pulse oximetry measures the relative transmission of light at two wavelengths that differ significantly when passed through loaded versus non-loaded hemoglobin (e.g., oxyhemoglobin versus deoxyhemoglobin). In order to provide values that correlate with arterial oxygen saturation levels as opposed to tissue bed or venous saturation levels, standard pulse oximeters require pulsatile blood to distinguish transmission at the peak of arterial pulsation relative to baseline transmission levels. Thus, pulse oximetry measurements will change both with changes in hemoglobin oxygen saturation and with conditions that interfere with the device's ability to detect pulsatile blood flow. Other conditions that alter pulse oximetry measurements by reducing the detection of fluctuations from arterial blood flow include peripheral vasoconstriction from hypothermia and vasopressor and interference from motion, such as tremors or shivering. Incorrect sensor application, highly calloused skin, and nail polish can also affect measurements by interfering with transmission readings. Because standard pulse oximetry only measures the relative difference in transmission between oxygenated and deoxygenated hemoglobin and not the absolute value of oxygenated hemoglobin, anemia does not significantly affect pulse oximetry values within physiologic ranges. Tachycardia, tachypnea, and fever do not directly affect pulse oximetry values.

Answer 66

The correct response is Option A. The patient has a presumed diagnosis of deep vein thrombosis (DVT) and pulmonary embolism (PE). Enoxaparin and rivaroxaban are contraindicated in patients with renal failure. Warfarin is used for long-term treatment of established DVT. Clopidogrel is an antiplatelet inhibitor that inhibits blood clots in coronary artery disease, peripheral vascular disease, cerebrovascular disease, and prevents myocardial infarction. Heparin is safe in renal failure patients and is indicated for treatment in acute DVT/PE.

Answer 67

The correct response is Option D. In this patient with septic shock, once airway and breathing are secured, the next most appropriate step in management is to restore effective circulation and perfusion to peripheral tissues starting with a trial of volume resuscitation with crystalloid. Signs of impaired end organ perfusion in septic shock include hypotension (e.g., mean arterial pressure \<70 mmHg), tachycardia (e.g., heart rate \>100 bpm), warm flushed skin giving way to cool clammy skin as blood flow is redirected to core organs, obtundation, and an elevated serum lactate concentration (e.g., \>1 mmol/L). First-line therapy for restoration of tissue perfusion is volume resuscitation using intravenous crystalloid targeted to physiologic end points while monitoring for clinical or radiographic evidence of either cardiogenic or non-cardiogenic pulmonary edema (ie, ARDS). The addition of pulmonary artery catheters has not been shown to improve outcomes in the routine management of septic shock and is associated with increased complications. As in the given scenario, evidence and expert opinion do not support the transfusion of blood products greater than a hemoglobin concentration of 7 g/dL in the absence of concurrent hemorrhagic shock, cardiac history, or active myocardial ischemia. For example, a recent multicenter randomized study involving 998 patients with septic shock reported no significant difference in mortality or rate of ischemic events between patients transfused when hemoglobin concentration was \<7 g/dL compared with patients transfused when hemoglobin was \<9 g/dL. Their former (more restrictive) transfusion trigger resulted in 50% fewer red blood cell transfusions compared with the more liberal strategy. Vasopressors (e.g., norepinephrine) are second-line agents in the treatment of septic shock refractory to trial of volume resuscitation as long as intravenous fluids successfully improve perfusion without impairing gas exchange. Inotropic agents (e.g., dobutamine) are also second-line agents to initial volume resuscitation in this scenario. They may be useful with refractory shock in the setting of diminished cardiac output.

Answer 68

The correct response is Option E. Accidental self-injection of epinephrine with an EpiPen occurs in 1 in 50,000 syringes. There have been no documented cases of digital necrosis following injection, and observation is indicated in this case. The effect of epinephrine’s vasoconstriction lasts for approximately 90 minutes and will likely resolve on its own. Phentolamine has been described as a reversal agent for epinephrine and has shown clinical efficacy, but there has been no study to show that there are better outcomes with phentolamine injection compared with observation. Also, the added volume of injection with phentolamine could cause pressure necrosis and the timing between EpiPen injection and definitive treatment would usually be outside of the 90 minutes it would take for the epinephrine to wear off on its own. Topical nitroglycerin paste and subcutaneous injection of calcium channel blockers such as nifedipine have not shown to be viable treatment modalities. Application of a hot pack can lead to increased tissue damage and burns and is not indicated. Emergent exploration is indicated for compartment syndrome and is not indicated in this case where the finger is soft.

Answer 69

The correct response is Option D. Risk factors for postoperative nausea and vomiting include: female gender, nonsmoking status, prior history of postoperative nausea/vomiting/motion sickness, use of volatile anesthetics/general anesthesia, opioid/narcotic use, facial rejuvenation procedures, and long duration of surgery. Several measures can be taken to decrease postoperative nausea and vomiting. A thorough history with identification of risk factors can aid stratification of patients preoperatively. Use of long-acting local anesthetic agents, nonsteroidal anti-inflammatory drugs (NSAIDs), and cyclooxygenase-2 selective inhibitors can decrease the need for postoperative opioid use. Avoidance of nitrous oxide, especially in combination with fentanyl and volatile inhalational gases, and multimodal use of serotonin antagonists combined with other antiemetic agents can also decrease postoperative nausea and vomiting.

Answer 70

The correct response is Option B. Higher American Society of Anesthesiologists (ASA) class has been identified as a risk factor for postoperative complications in HIV-positive patients in multiple studies. A patient who is ASA Class 2 has only mild systemic disease. Increasing class number indicates increasing severity of disease (Class 3 – severe systemic disease, Class 4 – severe systemic disease that is a constant threat to life). Acquired immunodeficiency syndrome (AIDS) is diagnosed when the CD4 count is \<200 cells/mm3 or with acquisition of an AIDS-defining illness. An absolute CD4 count of \<200 cells/mm3 has been associated with increased risk of complications including wound infections. HIV seropositivity alone has been found not to be an independent risk factor for postoperative complications. Percutaneous surgery, such as fat grafting, has not been associated with increased risk of infection in HIV patients, nor has skin incisional surgery. Transoral mucosal incisional surgery has been found to be associated with a significantly greater risk of wound infection in HIV patients. A viral load greater than 10,000 copies/mL suggests that antiretroviral therapy is no longer effective and has been identified as an independent risk factor for complications.

Answer 71

The correct response is Option D. Propofol can be safely used in patients with a suspected diagnosis of malignant hyperthermia. Malignant hyperthermia is a rare, life-threatening inherited skeletal muscle disorder that shows symptoms of hypermetabolic reaction to volatile anesthetic gases and depolarizing muscle relaxants. The incidence is between 1 in 5000 to 1 in 100,000 anesthetic encounters. Mortality rates have decreased from 70% to less than 5% as awareness of this condition has led to accurate diagnosis and treatment. Malignant hyperthermia is genetically transmitted through an autosomal dominant inheritance pattern with variable penetrance. In obtaining a medical history, it is important to document family history of adverse outcomes to general anesthesia. If it is reported that a first-degree relative has had a malignant hyperthermia crisis or susceptibility, then the patient should not be exposed to triggering agents. Anesthetic agents that trigger malignant hyperthermia include: halothane, enflurane, isoflurane, desflurane, sevoflurane, and succinylcholine. Nitric oxide can be used if the anesthesia machine is “vapor-free” and contains no traces of volatile gas. Other safe agents include nondepolarizing muscle relaxants (such as vecuronium, rocuronium, and pancuronium), all ester and amide local anesthetics, ketamine, propofol, etomidate, barbiturates, opiates, and benzodiazepines. Although it is safe to undergo minor procedures with administration of a topical or local anesthetic agent, patients undergoing complex procedures with intravenous sedation, general anesthesia, or major conduction blockade should be referred to an accredited ambulatory surgical center or hospital. If symptoms are recognized in the operating room (high temperature, increased end-tidal CO2, muscle rigidity), rapid treatment with dantrolene sodium is the highest priority. Acute episodes may require stopping the procedure and transfer to an intensive care unit.

Answer 72

The correct response is Option E. True allergic reactions to local anesthetics are rare. Type I hypersensitivity reactions may include anaphylaxis, and are modulated by immunoglobulin E. Both ester-based local anesthetics, such as procaine, and amide-based local anesthetics may induce an allergic response. The most likely allergen is para-aminobenzoic acid (PABA). This compound consists of a benzene ring substituted with an amino group at the 4-position (leading to the analogous label of 4-aminobenzoic acid) as well as a carboxyl group. Preservatives such as methylparaben have also been shown to cause allergic reactions to local anesthetics, but are less likely than allergic reactions caused by PABA. Epinephrine can induce vasoconstriction and increase the safe dosage of administered local anesthetic, though it would not be expected to cause an allergic response itself. Iodine and acetaldehyde should not be found in local anesthetic mixtures.

Answer 73

The correct response is Option B. Because lidocaine absorbs slowly from fat, infiltrate solutions that contain up to 35 mg/kg of lidocaine are generally considered safe. Nonetheless, lidocaine toxicity is still a risk of the procedure. In tumescent solution with epinephrine, peak plasma lidocaine levels occur approximately 10 to 14 hours after infiltration, and thus, the presentation 6 hours after discharge is consistent with peak plasma concentration. Lidocaine toxicity has symptoms of neurologic or cardiac toxicity. In the early stages, the complications are primarily neurologic and can include slurred speech, restlessness, tinnitus, and a metallic taste, as well as numbness of the mouth. As the concentrations increase, the neurologic concentrations become more severe, and can progress to muscle twitching, seizures, and cardiac arrest. Treatment of lidocaine toxicity is supportive. Fat embolism presents as a petechial rash, respiratory dysfunction, and cerebral dysfunction, and the symptoms usually appear 24 to 48 hours after surgery. Pulmonary embolism presents as leg pain and edema, tachycardia, and low-grade fevers. Parietal strokes usually cause sensory symptoms, self-perception anomalies, and left-right agnosia. Third spacing refers to fluid shifts into interstitial spaces and can cause edema, hypotension, and decreased cardiac output.

Answer 74

The correct response is Option A. Addition of local anesthetics during general anesthesia, whether by subcutaneous, tumescent, or regional block infiltration, can result in decreased dosage requirements of the common sedatives and analgesics that can result in nausea and emesis. Common anesthetic agents that promote nausea and emesis include opioids (fentanyl, hydromorphone, morphine) and inhalationals (halothane, isoflurane, nitrous oxide). Propofol is currently the most commonly used intravenous agent. It does not appear to directly result in nausea, but it has limited analgesic effects. Therefore, effective anesthesia with propofol requires addition of opioid narcotics (which cause nausea) and/or local anesthetics such as lidocaine and bupivacaine (which may decrease the narcotic requirement). Midazolam is a sedative-hypnotic that has anxiolytic and amnesic effects, both of which are helpful adjuncts to the surgical patient experience. Nausea is possible with midazolam, but less commonly reported than with narcotic and inhalational agents. The cause of postoperative nausea and vomiting is multifactorial and not fully understood. Strategies for prevention include: Recognition of high-risk patients (females, nonsmokers, history of motion sickness, previous postoperative nausea, general anesthesia) Pre- and postoperative treatment with multiple modalities (such as scopolamine, ondansetron, aprepitant, corticosteroids) Supplemental intraoperative oxygen and hydration

Answer 75

The correct response is Option D. The most appropriate management of acute bupivacaine toxicity is a bolus and infusion of 20% lipid emulsion. Every facility where local anesthetic is used in large doses should have a lipid rescue kit clearly labeled and available should the need arise. Although lipid rescue mechanism of action is not completely understood, it may be that the added lipid in the bloodstream acts as a “sink,” allowing for the removal of lipophilic toxins from affected tissues. Major local anesthetic toxicity can have such symptoms as sudden loss of consciousness, tonic-clonic seizures, hypertension followed by progressive hypotension, tachycardia, ventricular fibrillation, bradycardia, asystole, and cardiac arrest. Arrhythmias may be refractory to treatment, and resuscitation may be prolonged, sometimes requiring more than 1 hour. In the event of a local anesthetic toxicity event, airway management, seizure suppression, and, if needed, cardiopulmonary resuscitation should be performed. Alert the nearest facility having cardiopulmonary bypass capability and administer 20% lipid emulsion (values in parentheses are for 70 kg) as follows: Bolus 1.5 mL/kg intravenously over 1 minute (~100 mL) Continuous infusion 0.25 mL/kg/min (~500 mL over 30 minutes) Repeat bolus every 5 minutes for persistent cardiovascular collapse Double infusion rate if blood pressure returns but remains decreased Continue infusion for a minimum of 30 minutes Although beta-adrenergic blockers may be useful in treating the excitatory cardiovascular phase of local anesthetic toxicity, the potential to progress to more advanced phases with myocardial depression and collapse preclude their routine use. In addition to lipid emulsion, the treatment for local anesthetic–induced cardiac toxicity is generally supportive, and may include amrinone, closed-chest cardiac massage, and cardiopulmonary bypass. Flumazenil is used to reverse the effects of benzodiazepine toxicity. Dantrolene is administered in the acute treatment of malignant hyperthermia. Atropine and dopamine are administered as part of the Advanced Cardiac Life Support protocol for bradycardia or asystole and would not be used in the scenario described.

Answer 76

The correct response is Option D. Epinephrine use in hand surgery is becoming more common as is the inadvertent self-injection by people who carry epinephrine injectors (EpiPens). Typically, there is little treatment needed other than supportive care. However, when concern for tissue viability is raised or there is marked pain, subcutaneous phentolamine is the drug of choice to reverse the sympathomimetic effects of epinephrine. Plain lidocaine (typically 2% or more) will cause vasodilation but by a different mechanism than the reversal of the epinephrine. Topical nitroglycerin paste has been used for reversal of vasospasm, but again, a different mechanism is used. Marcaine is an amide anesthetic that inhibits sodium ion channels. It is not an antagonist of epinephrine.

Answer 77

The correct response is Option D. Signs and symptoms of lidocaine toxicity include dizziness, agitation, lethargy, tinnitus, metallic taste, perioral paresthesia, slurred speech, euphoria, hypotension, and bradycardia. Tachycardia is not a sign of lidocaine toxicity. Bradycardia is more common. Bronchospasm and urticaria are not signs of lidocaine toxicity.

Answer 78

The correct response is Option E. The most appropriate solution to infuse around the lesion to decrease intraoperative blood loss is 20 mL of 1:200,000 epinephrine. Although the maximum dose of subcutaneous epinephrine is unknown in a healthy child, large amounts have been shown to be safe in patients undergoing liposuction. The most conservative estimate for the amount of epinephrine (1:200,000) that can be safely injected in this child is 30 mL (3 mL/kg) every 10 minutes. Because this estimate was used in the past when halothane anesthesia was being administered (halothane lowered the arrhythmogenic threshold to epinephrine), greater volumes could likely be infused because other inhalational anesthetics are now used. Twenty mL of 1% lidocaine or 0.25% bupivacaine with epinephrine cannot be given to this 22-lb (10-kg) child because it exceeds the maximum dose. The maximum dose of lidocaine with epinephrine that can be administered is 7 mg/kg; because the concentration of 1% lidocaine is 10 mg/mL, only 7 mL of this solution could be injected. The maximum dose of bupivacaine with epinephrine that can be given is 3 mg/kg; because the concentration of 0.25% bupivacaine is 2.5 mg/mL, only 12 mL of this solution could be administered.

Answer 79

The correct response is Option C. The most appropriate next step in management is elevation of the extremity. Elevation facilitates venous return of the infiltrate, decreases swelling, and minimizes the risk of skin necrosis. The vasoconstrictive effects of epinephrine only last for 60 to 90 minutes; much longer ischemia times are necessary to cause skin necrosis. For example, amputated digits may be successfully replanted after 33 hours of warm ischemia time. The use of warm or cold compresses on an infiltration site is controversial. Heat may theoretically stimulate the evacuation of the infiltrate through vasodilation and increased blood flow. Ice may theoretically limit the inflammatory reaction as well as the diffusion of the infiltrated substance by causing vasoconstriction. However, warm or cold compresses may worsen tissue damage. Heat can cause thermal injury, and ice can cause ischemia from vasoconstriction, resulting in a “second hit” at the extravasation site. A partial-thickness skin injury may be converted to a full-thickness wound. Although phentolamine, an alpha-adrenergic antagonist, has been used to treat epinephrine infiltrations, the added volume of phentolamine can worsen the injury. Injection of an antidote adds more fluid to the subcutis and may increase the risk of pressure necrosis. In addition, because epinephrine causes vasoconstriction for only 60 to 90 minutes, its effects have usually worn off by the time the extravasation is noted, the patient is evaluated by a physician, the phentolamine is ordered, and the antidote is obtained from the pharmacy. Saline flush-out, using stab incisions through which saline is flushed, may be helpful for the infiltration of chemotherapeutic agents, but it requires several incisions and would be considered after elevation of the extremity.

Answer 80

The correct response is Option E. Postoperative nausea and vomiting (PONV) is a distressing complication of general anesthesia and occurs in 25 to 30% of surgeries. Oftentimes, multimodality treatment is implemented for prophylaxis. Transdermal scopolamine is a potential long-acting prophylactic antiemetic initially developed to prevent motion sickness but approved in 2001 by the US Food and Drug Administration (FDA) for the prevention of PONV. Scopolamine is a centrally acting anticholinergic agent and is designed as a patch placed behind the ear that will deliver 1.5 mg of scopolamine transdermally at a constant rate over 3 days. It has been shown to be effective in decreasing PONV for up to 24 hours after surgery. Several adverse events can occur including sedation, dry mouth, and blurred vision. In addition, mydriasis, usually ipsilateral to the side of patch application, can occur if direct contamination to the eye occurs from rubbing the eyes after manipulating the patch without hand washing. The diagnosis of scopolamine contamination can be confirmed by placing 0.5 to 1.0% pilocarpine hydrochloride in the affected eye. A dilated pupil from pharmacologic mydriasis will not constrict, whereas a dilated pupil from paralytic mydriasis will constrict. Misdiagnosis can result in an unnecessary and extensive workup for an intracranial etiology. The other options including dexamethasone, droperidol, metoclopramide, and ondansetron are effective antiemetic agents but have no anticholinergic profile.

Answer 81

The correct response is Option C. The patient is experiencing signs of early malignant hyperthermia, which is a life-threatening crisis and requires immediate attention. The typical symptoms of malignant hyperthermia are caused by a hypercatabolic state with increased heart rate, increased breathing rate, increased carbon dioxide production, increased oxygen consumption, acidosis, masseter muscle rigidity, and rhabdomyolysis. Very high temperature (110.0°F [43.0°C]) usually presents late. Even if treated properly, death may occur as brain damage, muscle damage, renal failure, and multiple organ failure ensue. The malignant hyperthermia crisis is a biochemical chain reaction response that is “triggered” by commonly used general anesthetics and the paralyzing agent succinylcholine within the skeletal muscles of susceptible individuals. Volatile gaseous inhalation anesthetics like sevoflurane, desflurane, isoflurane, and halothane can trigger malignant hyperthermia. The exact incidence of malignant hyperthermia is not known. Estimates vary from a frequency of one in 5000 to one in 65,000. Over 80 genetic defects have been associated with malignant hyperthermia. Malignant hyperthermia susceptibility is inherited with an autosomal dominant inheritance pattern. Children and siblings of a patient with malignant hyperthermia susceptibility usually have a 50% chance of inheriting a gene defect for malignant hyperthermia. The medical antidote is dantrolene. Additional methods include use of a hypothermia blanket (under/over the patient) and cold isotonic saline for intravenous solution.

Answer 82

The correct response is Option D. Managing anticoagulation in the perioperative period is challenging. The risk for thromboembolic phenomenon is transiently increased with any cessation in anticoagulation therapy. At the same time, this risk needs to be weighed against the risk for bleeding. For the patient described, who is high-risk for recurrent embolus (recent PE) and bleeding (due to the nature of the proposed procedure), these opposing risks need to be weighed carefully. They may be mitigated by a "bridging" strategy where short-acting agents provide prophylactic anticoagulation around the time of surgery while long-acting agents are held. While the decision to adjust anticoagulation therapy in the perioperative period is controversial, the mechanism of bridging therapies is based on the known pharmacokinetic behaviors of anticoagulation agents. The half-life of warfarin is approximately 36 hours, so stopping warfarin prior to surgery will allow the therapeutic INR to return to normal levels by the day of surgery. To maintain therapeutic anticoagulation, low-molecular weight heparin (LMWH) may be initiated 3 days prior to surgery as the INR decreases. In the absence of other factors that predispose the patient to bleeding events, warfarin may be safely resumed 1 to 2 days after surgery. Stopping warfarin 1 to 2 weeks prior to is unnecessary. Furthermore, a longer interval between cessation of warfarin and initiation of LMWH treatment may create a longer window where the patient is at risk for thromboembolic events. Stopping warfarin the day of surgery and initiating LMWH the same day will place the patient at an increased risk for bleeding.

Answer 83

The correct response is Option D. The advantages of Bier block include reliability with low incidence of block failure, safety with rapid onset and recovery. The block is limited to tourniquet pain often occurring after 20 to 30 minutes and limits its use to shorter procedures on the upper extremities. Sudden cardiovascular collapse or seizures may occur if local anesthetic is released into the circulation too early. Disease processes in which a tourniquet is contraindicated include Raynaud disease, sickle cell disease, and severe hypertension. Uncooperative patients and young children are also contraindications. Short duration procedures, including carpal tunnel release, tendon contracture release, foreign body extraction, and trigger finger release, are examples of procedures where Bier blocks may be considered. Age, gender, occupation, and urgency of surgery are not contraindications to this procedure. Bier block anesthesia is a contraindication in the very young and very old, but not in a 53-year-old patient.

Answer 84

The correct response is Option C. This is a case of inadvertent lidocaine toxicity with subsequent seizure and cardiac arrest. Furthermore, lipid emulsion has been used with apparent success early in the spectrum of local anesthetic systemic toxicity to preempt cardiac arrest. The role of lipid emulsion has expanded to treatment of cardiac toxicity due to other lipophilic drugs. Dantrolene is a treatment for malignant hypothermia. Dimercaprol is a chelating agent used for the treatment of heavy metal toxicities. N-acetylcysteine is used as a mucolytic and also in cases of acetaminophen overdose. Naloxone is used to treat narcotic overdose. There are no data to suggest that any of these medications are otherwise helpful in lidocaine toxicity.

Answer 85

The correct response is Option C. The most appropriate next step in management is elevation of the extremity. Elevation facilitates venous return of the extravasate, reduces swelling, and minimizes the risk of skin necrosis. The use of warm or cold compresses on the extravasation site is controversial. Heat may theoretically stimulate the evacuation of the infiltrate through vasodilation and increased blood flow. Ice may theoretically limit the inflammatory reaction, as well as the diffusion of the infiltrated substance, by causing vasoconstriction. However, warm or cold compresses may also worsen tissue damage. Heat can cause thermal injury, and ice can cause ischemia from vasoconstriction resulting in a ?second hit? at the extravasation site; a partial-thickness skin injury may be converted to a full-thickness wound. Although phentolamine, an alpha-adrenergic antagonist, has been used to treat epinephrine extravasation, the added volume of phentolamine can worsen the injury. Injection of an antidote adds more fluid to the subcutis and may increase the risk of pressure necrosis. In addition, because epinephrine causes vasoconstriction for only 60 to 90 minutes, its effects have usually worn off by the time the extravasation is noted, the patient is evaluated by a physician, the phentolamine is ordered, and the antidote is obtained from the pharmacy. Saline flush out, or using stab incisions through which saline is flushed, may be helpful for the extravasation of chemotherapeutic agents, but it requires several incisions and would be considered only after elevation of the extremity.

Answer 86

The correct response is Option D. The most appropriate local anesthetic to infuse at the wound site before repair is 1% lidocaine with 1:200,000 epinephrine. The addition of epinephrine to the local anesthetic increases the safety of the lidocaine and facilitates the laceration repair. Epinephrine slows the absorption of the local anesthetic, which allows lower doses to be used. Epinephrine also increases the duration of action of lidocaine, which provides longer pain relief. Vasoconstriction from the epinephrine reduces bleeding at the site of the injury, which shortens the operative time, lowers the risk of iatrogenic injury, and facilitates the repair. Epinephrine is not contraindicated in the fingers or toes. The vasoconstrictive effects of epinephrine only last for 60 to 90 minutes; much longer ischemia times are necessary to cause skin necrosis. For example, amputated digits may be successfully replanted after 33 hours of warm ischemia time. Although epinephrine diluted to a concentration of 1:1,000,000 (which is commonly used in tumescent solution for liposuction) will cause vasoconstriction, its onset is prolonged and its duration of action is shortened compared with epinephrine 1:200,000. Lidocaine or bupivacaine without epinephrine does not reduce bleeding at the site of injury, which increases the difficulty of the repair. In addition, without epinephrine, lower doses of local anesthetic must be used, and the patient has a shorter duration of pain relief.

Answer 87

The correct response is Option D. Ketamine can be administered intravenously or intramuscularly. Intravenous injection is generally safer, and has a lower rate of laryngospasm, shorter duration of clinical onset and effect, and lower rate of vomiting. It can be titrated with a continuous infusion or repeated boluses to effect.

Answer 88

The correct response is Option B. Malignant hyperthermia is a rare but potentially fatal sensitivity to volatile anesthetics and depolarizing neuromuscular blocking agents. A commonly used volatile inhalation agent is isoflurane. Succinylcholine is a depolarizing muscle relaxant frequently present in the operating room. When genetically susceptible individuals are given anesthesia with these agents, the classic findings include skeletal muscle rigidity, tachycardia, fever, cardiac arrhythmias, and metabolic and respiratory acidosis, leading to severe hypotension. Hyperthermia, the hallmark of malignant hyperthermia, is most often a late sign. The earliest signs are tachycardia and an increase in the end-expired carbon dioxide concentration. Dantrolene is not a trigger for malignant hyperthermia. It is the only drug recommended for the treatment of malignant hyperthermia. Propofol and nitrous oxide are not malignant hyperthermia triggers. Pancuronium is a non-depolarizing muscle relaxant and is therefore safe to use.

Answer 89

The correct response is Option D. The maximum dose of lidocaine with 1:100,000 epinephrine recommended for nontumescent injection is 7 mg/kg. In the 110-lb (50-kg) patient described, the maximum dose is 350 mg. One percent lidocaine with 1:100,000 epinephrine contains 10 mg per 1 mL; therefore, the maximum dosage for injection is 35 mL.

Answer 90

The correct response is Option D. The most appropriate next step in management is the administration of methylene blue as an antidote for methemoglobinemia. Methemoglobinemia is a clinical condition in which hemoglobin is unable to carry oxygen to end organs due to the formation of methemoglobin. Red blood cells contain four hemoglobin chains. Each hemoglobin molecule is composed of four polypeptide chains associated with four heme groups. The heme group contains an iron molecule in the reduced or ferrous form (Fe2+). By sharing an electron in this form, iron can combine with oxygen to form oxyhemoglobin. Hemoglobin can accept and transport oxygen only when the iron atom is in its ferrous form. When hemoglobin loses an electron and becomes oxidized, it is converted to the ferric state (Fe3+), or methemoglobin. Methemoglobin lacks the electron that is needed to form a bond with oxygen and, thus, is incapable of oxygen transport. Local anesthetics can act as oxidizing agents for the ferrous form of iron. Oxygenated blood is red, deoxygenated blood is blue, and blood containing methemoglobin is a dark, reddish brown color. This dark hue imparts clinical cyanosis when methemoglobin levels are at 1.5 g/dL (approximately 10 to 15% methemoglobin concentration); however, a level of 5 g/dL of deoxygenated blood is required for similar effects. Therefore, when methemoglobin levels are relatively low, cyanosis may be observed without cardiopulmonary symptoms. Normal methemoglobin concentrations are 1% (range of 0 to 3%). At concentrations of 3 to 15%, a slight discoloration (i.e., pale, gray, or blue) of the skin may be present. At concentrations of 15 to 20%, the patient may be relatively asymptomatic, but cyanosis is likely to be present. Signs and symptoms at concentrations of 25 to 50% include headache, dyspnea, light-headedness, weakness, confusion, palpitations, and chest pain. Cardiac arrhythmias, delirium, seizures, profound acidosis, coma, and death can occur at concentrations of 50 to 70%. Administration of supplemental oxygen, removal of the offending oxidizing agent, and the administration of the antidote methylene blue are the mainstays of therapy. Methylene blue acts to reduce the heme group from methemoglobin to hemoglobin. Most patients require only one dose. Resolution of toxicity should be seen within 1 hour, often within 20 minutes. The most appropriate dosage for adults is 1 to 2 mg/kg (0.1 to 0.2 mL/kg) intravenously over 3 to 5 minutes; the dose is repeated in 1 hour if continued symptomatology or significant methemoglobinemia is noted. The total dose should not exceed 7 mg/kg. Although there are reports of successful usage in neonates and infants, administration of methylene blue is not recommended for pediatric patients younger than age 6 years. For patients older than age 6 years, dosage is individualized; most cases reported in medical literature have utilized starting doses of 1 mg/kg either ntravenously, intramuscularly, or intraosseously over a period of 5 minutes. Most cases of local anesthetic-related methemoglobinemia have been associated with topical benzocaine (1 in 7000 bronchoscopies in one study). However, there are cases of lidocaine associated with this potentially fatal reaction in the literature, and knowledge of this is vitally important given the frequency with which plastic surgeons use this drug. Glucagon is an antidote for beta-blocker overdose, propranolol is a beta-blocker utilized in cardiac arrhythmias, insulin is used to decrease glucose levels or in scenarios of hyperkalemia, and dantrolene would be used in malignant hyperthermia.

Answer 91

The correct response is Option E. The clinical scenario describes tourniquet cuff leak leading to lidocaine toxicity. Factors that predispose to cuff leak during Bier block anesthesia include obesity (funnel-shaped arms) and hypertension. Initial signs of lidocaine toxicity include anxiety, tinnitus, and perioral numbness; muscular twitching, seizures, and respiratory or circulatory arrest may develop later. Critical initial management includes maintenance of the airway, oxygen ventilation, and intravenous fluid administration. Administering diphenhydramine intravenously and continuing with the procedure is inappropriate. Diphenhydramine should not be administered because the patient’s symptoms are not consistent with an allergic reaction. Deflating the tourniquet completely, waiting a few minutes to reperfuse the arm, then exsanguinating and reinflating the tourniquet, and deflating the tourniquet by 50 mmHg to ease the tourniquet pain, are both inappropriate. Deflating the tourniquet will worsen the patient’s condition by increasing the serum concentration of lidocaine. Administering bupivacaine (Marcaine) locally to manage the pain and continuing with the procedure is inappropriate because the underlying problem is not incisional pain. Continuing with the procedure without addressing the patient’s distress may lead to the development of more serious complications.

Answer 92

Please note: Upon further review, this item was not scored as part of the examination. The correct response is Option D. Generations of physicians, beginning in medical school, have been trained to avoid epinephrine use in fingers due to the fear of inducing ischemic necrosis. However, comprehensive literature reviews and large clinical outcome studies have failed to show any harmful effects resulting from the appropriate use of standard, current preparations of lidocaine with 1:100,000 epinephrine. The few cases of digital necrosis reported in the literature employed agents such as cocaine and procaine with undisclosed volumes of injection or concentrations of epinephrine. Large case series of common hand procedures, such as carpal tunnel surgery and tendon repair, support the safety of a local anesthesia-only, tourniquet-free approach. Tourniquets and upper extremity blocks, while generally very safe, are not without morbidity or complication. In patients who demonstrate excessive intraoperative blanching or concerning symptoms of ischemia, phentolamine can safely reverse the vasoconstrictive effects of epinephrine. In one study of over 3000 patients, not a single case required phentolamine reversal. Study authors recommend direct volar digital injections of 2 mL of local anesthesia. Up to 30 mL may be used in the wrist and hand and more in the forearm, if needed. The tumescent effect provides a fully anesthetic, bloodless field for optimal visualization. The use of local anesthesia should not impact tendon mobility. Intraoperative patient anxiety can occur in any awake patient, whether they receive local or regional anesthesia. In the numerous studies of local anesthesia hand surgery, patients appear to tolerate the procedure well. Avoiding tourniquet pain is particularly advantageous in patients who do not receive general anesthesia. The local anesthesia tumescent block technique should provide excellent analgesia and should not increase patient discomfort.

Answer 93

The correct response is Option B. The patient described has developed early postoperative pulmonary failure most likely caused by congestive heart failure. Perioperative fluids were administered with the assumption that the patient had normal cardiac function. Her history of long-standing hypertension, combined with postoperative studies that included the ECG showing left ventricular hypertrophy and chest x-ray study consistent with pulmonary edema, support diastolic dysfunction. Congestive heart failure is currently the leading admission diagnosis for medicine and cardiology hospital services. The main reason is the overlooked high prevalence of diastolic dysfunction secondary to long-standing systemic hypertension. Patients with hypertension and cardiac diastolic dysfunction have preserved left ventricular contractile function, but they also have hypertrophied ventricular muscle that is unable to maintain normal diastolic compliance. This can lead to higher left ventricular filling pressures, elevated atrial pressures, atrial distension, atrial arrhythmias, elevated postcapillary pulmonary pressures, ventilation/perfusion mismatches, and pulmonary and peripheral edema. Treatment involves afterload and preload reduction. Acute coronary syndrome is caused by an atherosclerotic plaque rupture blocking a coronary artery. The acute event is usually associated with chest pain and elevation of S-T segments on ECG. Pulmonary embolism is always a concern, but that usually occurs later in the postoperative period. Onset of symptoms is sudden and characterized by chest pain, respiratory distress, and anxiety. Pneumonia and chronic obstructive pulmonary disease exacerbation are not supported by the clinical history.

Answer 94

The correct response is Option E. Succinylcholine-induced hyperkalemia is most frequently observed in patients with large burns who have also had long hospitalizations. Without treatment, potentially fatal cardiac arrhythmias can occur. This condition is also observed in patients who have endured long hospitalizations for neurologic disorders, limiting mobility. Upregulation of acetylcholine receptors is thought to be responsible for the increased efflux of potassium from muscle cells when depolarizing neuromuscular blocking drugs such as succinylcholine are administered to such patients. Treatment includes supportive measures and administration of calcium, glucose, insulin, albuterol, furosemide, and/or sodium polystyrene sulfonate (Kayexalate), depending on the patient €™s symptoms. Benzodiazepines are widely used and well tolerated as anxiolytic agents in all types of patients. Burn patients are not at increased risk for side effects, and use of these agents preoperatively for the patient described would be appropriate. Although halothane can induce malignant hyperthermia, especially in combination with succinylcholine, this complication is caused by a genetic predisposition. Although intravenous barbiturates cause severe respiratory depression and drowsiness, prolonging the postoperative recovery, they are nevertheless safe in young patients, including a burn patient. Belladonna alkaloids are used to chemically lower the heart rate (atropine) and prevent nausea (scopolamine), and they are not contraindicated in a young, otherwise healthy burn patient.

Answer 95

The correct response is Option D. While it has been traditionally taught that the use of epinephrine-containing local anesthesia in performing digital blocks is to be shunned, recent peer-reviewed literature suggests that this is a potentially safe practice. There have been no reported cases of digital gangrene after commercially available lidocaine with epinephrine was introduced in 1948, except for reports of inadvertent iatrogenic injection with 1:1000 epinephrine. The previous reports of digital ischemic necrosis were all associated with older anesthetics, such as cocaine, eucaine, and procaine, which were mixed with epinephrine by hand. Furthermore, those older reports relate excessive volumes of injection, prolonged use of the tourniquet, use of hot soaks, and concomitant infection. Regardless of current practice or teaching, however, if an epinephrine-containing compound is to be administered to the digit, the surgeon must be familiar with how to reverse the pharmacologically induced vasoconstriction. In these situations, local infiltration of phentolamine, an alpha-receptor blocker, is able to reverse the effects of epinephrine and salvage the digits. Ingestion of low-dose aspirin will not counter vasoconstriction. It is an option for use in the replanted digit to help promote vascular patency, although this has not been definitely proven. Although application of warm compresses is a potential treatment for hypothermia-induced vascular embarrassment, it would not reverse the pharmacologically induced effects of the epinephrine, and therefore is not the most appropriate choice for the patient described. Elevation of the hand will not reverse the epinephrine-induced vasospasm. Topical administration of a calcium channel blocker, such as papaverine, would also not have the desired effect of reversing epinephrine-induced vasospasm when applied as described. Topical administration has been used in digital replantation to help reverse vasospasm. However, in the scenario described, the digital vessels are not exposed, and direct injection of a reversal agent is the most appropriate, direct method of addressing this situation.

Answer 96

The correct response is Option E. A nerve block at the cubital tunnel, through which the ulnar nerve passes, will provide appropriate anesthesia for the ulnar nerve, but not for the median nerve, which passes anterior to the cubital tunnel at the elbow and through the carpal tunnel at the wrist. This would not provide sufficient anesthesia to perform carpal tunnel release. Both general anesthesia and regional anesthesia with a Bier block are acceptable choices for use in hand surgery. When used in hand surgery, local anesthesia with epinephrine has been documented to be safe, despite incorrect dogma that epinephrine is dangerous in this anatomical region. Several recent critical analyses demonstrate that epinephrine neither causes significant ischemia in the hand nor risks digital infarction.

Answer 97

The correct response is Option E. Postoperative nausea and vomiting (PONV) is a multifactorial entity, comprising patient, surgical, and anesthetic factors. Attempts have been made to identify the risk factors. A recent study concluded that female gender, a history of motion sickness or PONV, nonsmoking status, and use of postoperative opioids were most predictive. The incidences of PONV with the presence of zero, one, two, three, or all four of these risk factors were 10%, 21%, 39%, 61%, and 79%, respectively. Some surgical procedures are associated with a higher incidence of PONV, eg, major breast procedures, strabismus surgery, laparoscopy, and laparotomy. Agents used during anesthesia, including opioids, nitrous oxide (N2O), and volatile inhalational anesthetics, are emetogenic. Pain, anxiety, and dehydration may also increase the incidence of PONV. Propofol is widely used in ambulatory surgery because of its favorable clinical characteristics, including rapid recovery and minimal PONV. When compared with propofol, sevoflurane is associated with a higher incidence of PONV. Etomidate has minimal cardiovascular side effects, but it has a high incidence of PONV and is not commonly used in outpatient anesthesia. Nitrous oxide has been found to increase PONV when used as a primary anesthetic agent but not when used in combination with other agents. Intravenous anesthesia with ketamine has a lower risk of pulmonary aspiration but may result in higher rates of PONV.

Answer 98

The correct response is Option D. EMLA (eutectic mixture of local anesthetic) is a highly effective method of inducing topical anesthesia. A eutectic mixture consists of two substances that when mixed have a lower melting point than either substance alone. EMLA uses a combination of lidocaine and prilocaine. It has excellent penetration and produces remarkably little sensitivity reaction. The efficacy of EMLA varies according to the relative thickness of the skin and its vascularity. The cream is applied fairly thickly (1-2 g of EMLA per 10 cm2 of skin) and a dressing such as Opsite or Tegaderm is used to keep it in place. Gentle regular massage to the area can be applied for at least an hour.

Answer 99

The correct response is Option E. Malignant hyperthermia is an inherited myopathy characterized by a hypermetabolic state when the patient is exposed to an appropriate triggering agent, such as all inhalational agents or depolarizing muscle relaxants (ie, succinylcholine). Initial presentation is usually an unexplained tachycardia, followed by an increase in end-tidal carbon dioxide, decrease in oxygen saturation, dysrhythmia, and muscle rigidity. Hyperthermia occurs but can be a late finding. The most appropriate management involves calling for assistance, stopping all triggering agents, hyperventilating with 100% oxygen, administering dantrolene, stopping all surgery, volume resuscitating, and correcting hyperkalemia.Removal of prostheses and administration of antibiotics are not appropriate because this is not a toxic shock syndrome. Bilateral pneumothoraces are unlikely, although they should be ruled out. Pulmonary embolism is unlikely in the young patient described during a fairly short operation (very low risk).

Answer 100

The correct response is Option C. Long operative times and significant surface area exposure are often required in body contouring procedures following massive weight loss. These factors may contribute to decreases in core body temperature. Actively maintaining intraoperative normothermia allows patients to maintain normal coagulation function during elective plastic surgery lasting longer than two hours, potentially reducing the occurrence of bleeding-related complications.It has been recommended that ambient room temperatures for these cases be kept no less than 70 °F (21.1 °C). Additionally, as much of the body as possible should be covered to reduce heat loss. Additional measures to maintain normothermia include fluid-filled warming blankets placed under the patient on the operating table, warming of intravenous fluids, head and foot stockings, and forced-air warming blankets.

Answer 101

The correct response is Option B. Dantrolene is the only clinically available drug for the specific treatment of malignant hyperthermia. Malignant hyperthermia is a rare but potentially fatal sensitivity to volatile anesthetics and depolarizing neuromuscular blocking agents. When genetically susceptible individuals are given anesthesia with these agents, the classic findings include skeletal muscle rigidity, tachycardia, fever, cardiac arrhythmias, and metabolic and respiratory acidosis, leading to severe hypotension. Hyperthermia, the hallmark of malignant hyperthermia, is most often a late sign. The earliest signs are tachycardia and an increase in the end-expired carbon dioxide concentration. With the use of dantrolene, the mortality from malignant hyperthermia decreased from 80% in 1960 to less than 10%. Dantrolene is a skeletal muscle relaxant that depresses the intrinsic mechanisms of excitation-contraction coupling. The mainstay of treatment for malignant hyperthermia includes discontinuance of the inciting anesthetic agents, rapid body cooling, and dantrolene. Rapid dantrolene preparation and infusion are critical. Therapy is started by continuous rapid intravenous push beginning at a dose of 1 mg/kg to 2.5 mg/kg and continuing until symptoms subside or the maximum cumulative dose of 10 mg/kg is reached. If symptoms reappear, the regimen may be repeated. Dantrolene is packaged in powdered form as a 20-mg vial which must be reconstituted with 60 mL of sterile water for injection (without a bacteriostatic agent). Acidic solutions such as 5% dextrose and 0.9% sodium chloride should not be used. The effective dose to reverse the crisis will vary in each individual. Pediatric dosing is the same as for adults. Care must be taken during infusion to avoid extravasation because there is a possibility for tissue necrosis because of the high pH. Malignant hyperthermia may not occur during the first exposure to an anesthetic triggering agent, but it may develop during subsequent operations. Symptoms range from mild to life-threatening hyperthermic crisis. The only screening test for susceptibility is through muscle biopsy. Dantrolene should be administered preoperatively to patients prone to malignant hyperthermia; anesthetic drugs that are known to trigger malignant hyperthermia should be avoided. Medications considered safe for patients susceptible to malignant hyperthermia include both lidocaine and bupivacaine. General anesthesia can be performed with alternative anesthetic regimens including nondepolarizing paralytic agents, nitrous oxide, and opioids (eg, vecuronium, propofol [Diprivan], and fentanyl). Dobutamine is an inotropic agent that may be used to support circulation in severe malignant hyperthermia, but it is not specific for the disease. Dicyclomine is an anticholinergic used to treat irritable bowel syndrome. Darifenacin is a muscarinic receptor antagonist used to treat overactive bladder. Dalteparin is a low-molecular-weight heparin used as deep vein thrombosis prophylaxis.

Answer 102

The correct response is Option E. The most likely cause of change in electrocardiography in the patient described is vasoconstriction of the epicardial coronary arteries caused by a toxic dose of cocaine. The maximum safe dose of cocaine is 1.5 mg/kg, or 100 mg in a 70-kg adult. The patient described received a topical dose of 400 mg. With an average 37% mucosal absorption rate, the absorbed dose is still approximately 150 mg. Cocaine increases myocardial oxygen demands via alpha €‘adrenergic stimulation and decreases myocardial oxygen supply through vasoconstriction of the coronary arteries, resulting in myocardial ischemia. Adverse cardiovascular reactions are possible after the administration of local anesthetics. At toxic levels, lidocaine and bupivacaine block sodium channels in cardiac tissue, resulting in a depressed rate of depolarization during phase 0 of the cardiac action potential. This manifests as prolonged QRS width, depression of left ventricular function, and ventricular arrhythmias from increased activity in reentrant pathways. Hypersensitivity reactions to local anesthetics usually result in a shock-type scenario with hypotension, although histamine can cause coronary artery spasm. High doses of epinephrine can cause hypertension through increased peripheral vascular resistance. The doses of lidocaine, epinephrine, and bupivacaine that were administered to the patient described were within the range of maximum recommended doses.

Answer 103

The correct answer is Option E. Actual hypersensitivity is rare and accounts for less than 1% of all reactions to local anesthetics. Allergic reactions may be attributed to other factors such as acute toxicity (eg, high plasma levels caused by inadvertent intramuscular injection), psychomotor reactions (eg, patient anxiety or apprehension), pharmacologic properties of local anesthetics, concurrent drug therapy (eg, epinephrine-induced tachycardia), or preservatives such as paraben or sulfites, which may be present in multidose vials. Local anesthetics with a para €‘aminobenzoic acid (PABA) ester €‘type structure seem to cause most anesthesia €‘related allergic reactions. Documented cross €‘sensitivity has been exhibited within the ester €‘based family of local anesthetics and structurally related compounds (eg, paraben preservatives). PABA is structurally similar to methylparaben. Amide local anesthetics do not metabolize to PABA; therefore, hypersensitivity to amide local anesthetics is rare. Because of possible hypersensitivity, many manufacturers have reformulated some of their products to eliminate methylparaben. Some of these products include Nesacaine-MPF (methylparaben-free), Xylocaine MPF, Polocaine MPF, and Sensorcaine MPF. A ruling by the United States Food and Drug Administration mandated the removal of methylparaben from all local anesthetic dental cartridges. Antioxidants (sodium bisulfite, metabisulfite) are added to local anesthetic products that contain vasoconstrictors (epinephrine, levonordefrin) to prevent biodegradation by oxygen.

Answer 104

The correct response is Option B. In the scenario described, a medication error has apparently occurred. A staff member has probably misread the surgeon's formula for local anesthetic and used bupivacaine in place of lidocaine. Surgeons should be encouraged to prepare their own solutions and read all labels on the medications they use, but in practice, nurses often prepare wetting solutions and injection solutions, and, even in the best of facilities, errors may occur. The accepted maximum dose of bupivacaine is 2.5 mg/kg, and thus anything over 150 mg is considered toxic in a 50-kg patient. The patient described was given 50 ml of a 0.5% solution, which contains 5 mg/ml of medication. Therefore, she was given 250 mg of the medication, well into the toxic range. On the other hand, had she been given lidocaine 0.5% with epinephrine, the maximum dosage would have been 7 mg/kg, or 350 mg of lidocaine. The amount of lidocaine in 50 ml of a 0.5% solution is 250 mg, within the safe zone for this patient. If the solution had been mixed as intended, the patient described would have received 250 mg of lidocaine and 25 mg of bupivacaine, and the resulting total amount would have been within the safe zone and well below the toxic range. Large doses of bupivacaine can cause irreversible, nonrecoverable heart block (a recent case in Australia involved placing the patient on cardiac bypass until the toxicity was resolved [Soltesz, et al. 2003]). Recent literature has indicated that intralipid (1 ml/kg of a 20% solution IV recommended by Weinberg) is important in reducing mortality (Weinberg, et al. 1998, 2003, 2006; Rosenblatt, et al. 2006). Discussion at recent anesthesiology meetings has resulted in the recommendation that all facilities using bupivacaine also be stocked with intralipid (Dr. P. Schneider, anesthesiologist, personal communication). It is essential to realize that transfer to a hospital center for further treatment is urgent and mandatory in bupivacaine overdose and that immediate transfer without delay offers the best chance of survival, as further absorption from injected tissues is to be expected during this critical period (Mather, et al. 2005). The dosages of benzodiazepine, lidocaine, and opiates are all appropriate in the scenario described. The ECG changes are consistent with bupivacaine toxicity, not heart ischemia.

Answer 105

The correct response is Option A. One of the key principles of this operation is safety in the amount of local anesthesia used and the timing of injection. The absorption of lidocaine from above the clavicles peaks at approximately five to six hours when injected into the neck via tumescent solution. The absorption of the tumescent peaks at approximately 12 hours for the trunk region (the thighs in the reference below). If the tumescent is given for the abdomen and several hours later for the face and neck, then the lidocaine absorption curves could be superimposed and reach a toxic level. An immediate bolus of all the local anesthetics may not be preferred for a similar reason, as the absorption curve might peak. The epinephrine will be needed in the local anesthetic to delay rapid absorption via vasoconstriction and should not be eliminated if larger doses of local anesthesia are needed, although the epinephrine and local dose can be diluted to give a similar vasoconstrictive effect. Local anesthetics are additive in their risk and have a certain degree of cross-reactivity in their doses. Mixing a less-than-toxic dose of bupivacaine plus a less-than-toxic dose of lidocaine can add to a toxic effect. If large procedures are to be considered under local anesthesia and toxic doses limits are being approached, the surgeon should consider separating operative dates or another choice of anesthesia.

Answer 106

The correct response is Option C. The U.S. Food & Drug Administration (FDA) has classified drugs according to their risk during pregnancy. The classifications are as follows: Category A: Controlled studies in women fail to demonstrate a risk to the fetus in the first trimester (and there is no evidence of a risk in later trimesters). The possibility of harm to the fetus seems remote. Category B: Either animal-reproduction studies have not demonstrated a risk to the fetus but there are no controlled studies in pregnant women, or animal-reproduction studies have shown an adverse effect (other than a decrease in fertility) that was not confirmed in controlled studies in women in the first trimester (and there is no evidence of a risk in later trimesters). Category C: Either studies in animals have shown adverse effects on the fetus (teratogenic or embryocidal or other) and there are no controlled studies in women, or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the fetus. Category D: There is positive evidence of risk to the fetus in humans, but the benefits from use in pregnant women may be acceptable despite the risk (e.g., if the drug is needed in a life-threatening situation or for a serious disease for which safer drugs cannot be used or are ineffective). Category X: Studies in animals or humans have demonstrated fetal abnormalities or there is evidence of risk to the fetus based on human experience, or both, and the risk of the use of the drug in pregnant women clearly outweighs any possible benefit. The drug is contraindicated in women who are or may become pregnant. There is a some evidence that diazepam and other benzodiazepines are teratogenic in humans, increasing the risk of congenital malformations when ingested by the mother during the first trimester of pregnancy. Diazepam is in the FDA pregnancy category D; the other drugs listed are not. Emergency surgery that requires anesthesia must be taken into consideration because there is a likelihood of initiating labor due to stress and because there is also a risk of drug-induced fetal defects, especially during the first trimester. The anesthetic technique of choice is regional anesthesia. Chloroprocaine is hydrolyzed quickly and, therefore, becomes unavailable for transfer across the placenta. Bupivacaine is strongly bound to protein and, therefore, very little drug is available for transfer across the placenta. If systemic drugs need to be given, morphine and fentanyl are preferred.

Answer 107

The correct response is Option C. Lidocaine for local infiltration is available in 0.5%, 1%, 1.5%, and 2% solutions that contain epinephrine at a concentration of 1:100,000 or 1:200,000. In contrast, lidocaine for tumescent anesthesia commonly is available in a 0.05% solution that contains epinephrine at a concentration of 1:1,000,000. This dilute solution results in a very slow rate of lidocaine absorption from subcutaneous tissue, which prevents high peak plasma concentrations of the drug as well as toxicity. Although a standard 1% solution yields a maximum plasma concentration of lidocaine in 1 hour, a tumescent solution provides a maximal plasma concentration in 8 to 12 hours. The chemical structure of lidocaine can vary with the pH of the tissue. However, this is not a primary factor in the pharmacokinetics of tumescent lidocaine. Suction lipectomy removes some lidocaine, which reduces the peak plasma concentration by approximately 25% (compared with a nonBsuction-lipectomy control). However, this is not the primary mechanism that allows a fivefold increase in dose without toxicity. In human studies of the toxic threshold for plasma lidocaine, central nervous system symptoms occurred at concentrations above 4 \_g/mL; this was equally true for standard and tumescent solutions.

Answer 108

The correct response is Option C. True allergic reactions to local anesthetics, although rare, can occur with the ester-linked agents chloroprocaine, tetracaine, procaine, and benzocaine. The degradation product of ester-linked anesthetics is para-aminobenzoic acid (PABA), which is an antigenic substance. The amide-type anesthetics lidocaine, bupivacaine, mepivacaine, and prilocaine do not cause true allergic reactions. Allergic reactions to amide-type anesthetics may occur but are usually related to the preservative methylparaben, which is structurally similar to PABA.

Answer 109

The correct response is Option A. Blood pressure is typically insensitive to increasing plasma levels of lidocaine and other local anesthetics because a compensatory increase in systemic vascular resistance prevents the blood pressure from increasing. Adverse reactions in the central nervous system are much more common and are biphasic. Initially, an excitatory phase occurs, which may be due to inhibition of the amygdala. This phase may produce muscle twitching in the face and extremities followed by tremors that can progress to seizures. As the amount of local anesthetic increases, a depressive phase occurs and is characterized by drowsiness, unconsciousness, and respiratory arrest. The cardiovascular system is thought to be more resistant than the central nervous system to the effects of local anesthetics. However, it can sustain dangerous reactions, usually at higher plasma levels. With toxic doses of local anesthetics, cardiovascular reactions may include arrhythmias, cardiovascular depression, and shock. Cardiovascular depression tends to be serious and difficult to treat. The more lipid-soluble local anesthetics, such as bupivacaine, tend to have a higher toxicity than the less lipid-soluble drugs, such as lidocaine. Toxic effects of local anesthetics result from inappropriately high dosage or unintentional intravascular injection. Management of lidocaine toxicity consists of ECG monitoring and oxygen administration. If seizures occur, they are typically controlled with diazepam or midazolam. If mechanical ventilation is required, paralytic agents may be administered. Because of the seriousness of the toxic effects, appropriate monitoring and personnel trained in advanced cardiac life support are required during local anesthetic use, regardless of the magnitude of the procedure.

Answer 110

The correct response is Option D. The pharmacokinetic properties of local anesthetics, including lipid solubility, pKa, protein binding, and nonspecific tissue binding, determine their clinical characteristics. The duration of action correlates directly with protein binding; ie, greater protein binding results in a longer duration of action. This best explains the long duration of action of bupivacaine when compared with lidocaine; bupivacaine has been shown to be 96% protein-bound, while lidocaine is 64% protein-bound. The lipid solubility of a local anesthetic determines its potency. Higher solubility leads to a higher potency drug. Bupivacaine has a longer onset of action (5 to 8 minutes) than lidocaine (2 to 4 minutes), but its duration of action (up to 10 hours) is much longer than that of lidocaine (up to 3 hours). This small difference in onset of action does not account for the prolonged duration of action. The pKa is defined as the negative logarithm of the acid ionization constant. This determines the onset of action of a local anesthetic because the uncharged (or base) form is the active component. Local anesthetics with a high pKa have the slowest onset of action because the pKa varies more greatly from the physiologic pH of the drug. Lidocaine, with a pKa of 7.9, has a more rapid onset of action than bupivacaine, which has a pKa of 8.1. Addition of epinephrine, a vasoconstrictor, to a local anesthetic prolongs the duration of action of the anesthetic and decreases its toxicity. However, all local anesthetics, with the exception of cocaine, have natural vasodilator activity.

Answer 111

The correct response is Option B. In otherwise healthy children older than 3 years of age who have normal lean body mass, the maximum safe dose of lidocaine (Xylocaine) that can be administered is determined by the child’s age and weight. The maximum safe dosage in a 22-kg 5-year-old child is 22 multiplied by 4.5, or 100 mg of lidocaine. At a 1% concentration, which contains 10 mg lidocaine per milliliter (mL), the maximum dose is 10 mL, according to the manufacturer’s recommendation.

Answer 112

The correct response is Option E. All local anesthetics can be classified as either ester- or amide-type. Ester-type local anesthetics, including procaine, benzocaine, chloroprocaine, and tetracaine, can produce allergic reactions. These anesthetics are metabolized by pseudocholinesterase, forming para-aminobenzoic acid (PABA). This compound triggers antibody formation and lymphocyte stimulation to elicit a hypersensitivity reaction. In one study of patients who had no known history of allergy to local anesthetics, 30% of patients developed a positive skin reaction following intradermal injection of an ester-type anesthetic. Amide-type local anesthetics, including bupivacaine, etidocaine, lidocaine, and mepivacaine, are used more frequently for local infiltration than ester-type agents. These are stable solutions that do not cause true allergic reactions. Any “allergic” reaction to amide-type local anesthetics is most likely caused by methylparaben, a preservative that is structurally related to PABA. Preservative-free local anesthetics are currently available for use in any patient who has sensitivity to methylparaben. In the same study mentioned above, there were no allergic reactions to the amide-type agents. A trick to help remember which complexes belong to which group is that all amides have an “i” in the prefix before the “caine” (ie, bupivacaine, etidocaine, lidocaine, and mepivacaine).

Answer 113

The correct response is Option E. Because EMLA cream reaches its peak efficacy approximately 45 to 60 minutes after initial application, the surgeon should wait for one hour before suturing the laceration. Studies show that EMLA cream is superior for anesthesia of simple extremity wounds and results in optimal anesthesia in open wounds after approximately 60 minutes. Cumulative sum (CUSUM) analysis has been used to confirm the minimal effective application time. EMLA cream, a eutectic mixture of local anesthetics, contains lidocaine 5% and prilocaine 5%. Following topical application of EMLA cream, the affected site should be covered with an occlusive dressing.

Answer 114

The correct response is Option B. While all the symptoms listed are present in a full-blown episode of malignant hyperthermia, increased end-tidal CO2 concentration and unexplained tachycardia are generally seen as the earliest presenting signs. Fever, metabolic acidosis, hyperkalemia with electrocardiographic changes, myoglobinuria, and cardiac arrest are late signs. Malignant hyperthermia is a pharmacogenetic disorder triggered by certain volatile anesthetic gases (eg, isoflurane, sevoflurane, desflurane) and depolarizing agents like succinylcholine. It affects skeletal muscle in affected individuals, causing unregulated calcium release from the sarcoplasmic reticulum of muscle cells after triggering. Malignant hyperthermia may present after induction, during anesthesia, or even in the postanesthesia care unit. Dantrolene is the only effective treatment. The Malignant Hyperthermia Association of the United States has valuable resources on this topic. Their 24-hour crisis hotline is 1-800-644-9737, which can be helpfully posted in every operating room. Malignant hyperthermia drills should be part of the training policy for every surgery center accredited by the American Association for Accreditation of Ambulatory Surgery Facilities.

Answer 115

The correct response is Option B. Conscious sedation, or moderate sedation, involves modification of the level of consciousness through pharmacologic administration. Patients can respond to verbal commands and protect the airway without support. Spontaneous respiration and cardiovascular function are not impaired. To ensure safety, health care providers often have specific training and/or certification to perform conscious sedation. Preparation is paramount. This includes monitoring devices, necessary medications, supplemental oxygen, and airway interventions, in the event of complication or accidental transition into deep sedation. Midazolam overdose may cause loss of consciousness or respiratory depression. The reversal agent is flumazenil, which is administered intravenously. The dose in adults is 0.2 mg/dose, to a total of 3 mg, over 30 seconds, followed by 0.3 mg to 0.5 mg at 1-minute intervals to a maximum dose of 3 mg. Naloxone is an opioid antagonist. It can be used to reverse the effects of fentanyl, which is commonly used in conscious (moderate) sedation. However, a narcotic was not part of this patient's care. Neostigmine is an anticholinesterase used for the reversal of neuromuscular blockade. Dantrolene is not a reversal agent per se, but it is used to treat malignant hyperthermia because of its muscle relaxant properties. Sugammadex is the first selective relaxant binding agent for reversal of neuromuscular blockade induced by rocuronium or vecuronium. Treatment of propofol-induced hypoventilation is mask ventilation and oxygen.

Answer 116

The correct response is Option D. Coronavirus disease 2019 (COVID-19) infection can lead to cardiovascular complications, particularly in those with pre-existing risk factors. Catastrophic adverse events include acute coronary syndrome, arrhythmias, myocarditis, heart failure, and pericardial tamponade (Mohammed Sheata et al). Viral infections have been implicated in causing pericardial tamponade, and COVID-19—associated pericardial tamponade may be due to a systemic inflammatory response. Coexisting renal impairment may also increase risk. Acute pericardial tamponade carries a high mortality rate; therefore, diagnosis and treatment is paramount. Patients most commonly complain of dyspnea if they are not obtunded from an acute cardiac event. The Beck triad includes: falling arterial pressure, rising venous pressure, and a "small, quiet heart." Short-term survival depends on early diagnosis and treatment (Alerhand et al). Bedside pericardiocentesis should be considered with acute deterioration in hemodynamic parameters (Tsang et al). Because the patient is experiencing cardiac tamponade, urgent assessment of other organ systems would be incorrect.

Answer 117

The correct response is Option B. Treatment for hyperkalemia has traditionally been organized into stabilizing the cardiac depolarization threshold, shifting potassium intracellularly, and eliminating total body potassium. The urgency of treatment often depends on electrocardiography (ECG) findings. In this scenario, the patient has acute hyperkalemia with peaked T-waves. Because of the potential for cardiac arrhythmias in the setting of rapid ECG changes, urgent treatment of hyperkalemia is necessary. The first step in management of hyperkalemia involves stabilization of the cardiac membranes using calcium gluconate or calcium chloride. This has a rapid onset of action (1 to 2 minutes), protects the cardiac myocytes, and is expected to decrease the serum potassium concentration by 0.5 to 1.5 mEq/L. Once the immediate threat of cardiac arrhythmia has been mitigated, shifting the potassium intracellularly is the next priority. This can be accomplished by an intravenous bolus of regular insulin, the use of inhalational beta-agonists (albuterol), or, in patients with concomitant metabolic acidosis, administration of sodium bicarbonate. Definitive elimination of potassium from the body is accomplished by using an exchange resin (sodium polystyrene sulfonate) or by hemodialysis (Mushiyakh et al, Lemoine et al). Use of sodium polystyrene sulfonate with sorbitol has limited evidence for its efficacy and has been shown to cause colonic necrosis (Gupta et al).

Answer 118

The correct response is Option B. This patient has septic shock, which is hemodynamically characterized by peripheral vasodilation leading to a substantial decrease in peripheral vascular resistance. During sepsis, bacterial debris and proinflammatory mediators (such as tumor necrosis factor alpha and histamine) cause peripheral vasodilation. In the initial stage of septic shock, this sudden increase in vascular volume or capacity is not matched by the relatively unchanged volume of circulating blood, leading to relative hypovolemia (not hypervolemia), decreased venous return to the heart, and decreased cardiac output. This is the hypodynamic phase of septic shock. It may be difficult to differentiate it from hemorrhagic (truly hypovolemic) shock, at least until fluid resuscitation is administered. Relative hypovolemia may persist even after fluid resuscitation, as the heart is unable to keep up with the degree of arterial vasodilation, despite increased central venous pressure. The hyperdynamic phase of shock follows initial fluid resuscitation. During this phase, cardiac output increases in an attempt to compensate for the decrease in peripheral vascular resistance caused by ongoing peripheral vasodilation. At this stage, vasopressors such as norepinephrine can be instrumental in mitigating vasodilation and maintaining an acceptable blood pressure to ensure end-organ perfusion (recommended mean arterial pressure of at least 65 mmHg). Proinflammatory mediators in sepsis also cause increased capillary permeability (leading to extravasation of intravascular volume into the interstitial tissues and anasarca), decreased myocardial contractility (weaker myocardial contraction leading to decreased output per heartbeat), and decreased end-organ microvascular perfusion (due to dysfunction/contraction of precapillary vascular sphincters causing arteriovenous shunting).

Answer 119

The correct response is Option B. The latest version of the American Society of Anesthesiologists (ASA) Physical Status Classification System was approved by the ASA House of Delegates on October 15, 2014, and has been updated in December 2022. No specific classification is assigned to patients with moderate systemic disease; there are only assignments for patients with mild systemic disease (ASA II) and those with severe systemic disease (ASA III). ASA I: a normal, healthy patient. Example: fit, nonobese (BMI under 30 kg/m2) patient who does not smoke cigarettes and has good exercise tolerance. ASA II: patient with mild systemic disease. Example: patient with no functional limitations and a well-controlled disease (eg, treated hypertension, obesity with BMI under 35 kg/m2, frequent social drinker, or cigarette smoker). ASA III: patient with a severe systemic disease that is not life-threatening. Example: patient with some functional limitation due to disease (eg, poorly treated hypertension or diabetes, morbid obesity, chronic renal failure, a bronchospastic disease with intermittent exacerbation, stable angina, or implanted pacemaker). ASA IV: patient with a severe systemic disease that is a constant threat to life. Example: patient with functional limitation from severe, life-threatening disease (eg, unstable angina, poorly controlled chronic obstructive pulmonary disease, symptomatic congestive heart failure, recent [less than 3 months ago] myocardial infarction or stroke). ASA V: moribund patient who is not expected to survive without the operation; the patient is not expected to survive beyond the next 24 hours without surgery. Example: ruptured abdominal aortic aneurysm, massive trauma, or extensive intracranial hemorrhage with mass effect. ASA VI: a brain-dead patient whose organs are being removed with the intention of transplanting them into another patient. The addition of "E" to the ASA physical status (eg, ASA IIE) denotes an emergency surgical procedure. The ASA defines an emergency as existing "when the delay in treatment of the patient would lead to a significant increase in the threat to life or body part."

Answer 120

The correct response is Option C. Postoperative nausea and vomiting (PONV), which is nausea and/or vomiting occurring within 24 hours of surgery, affects nearly one third of patients and can result in hematoma, incisional dehiscence, aspiration, prolonged pain, longer hospital stays, and patient dissatisfaction. Primary control of nausea and vomiting arises from the vomiting center located in the medulla. Risk factors include female sex, prior history of motion sickness or PONV, nonsmoker status, and the use of postoperative opioids. Prophylactic measures may decrease the risk for PONV, including preoperative, intraoperative, and postoperative medications. Of the options listed, only propofol has been shown to decrease the risk for PONV when administered during induction. Thiopental is a barbiturate that produces a "hangover"-like effect and PONV. Nitrous oxide is an inhalational agent that is associated with PONV. Remifentanil hydrochloride is a short-acting narcotic and can cause PONV. Halothane is a volatile anesthetic, which is known to cause PONV.

Answer 121

C The patient has HIV-associated facial lipodystrophy. This is characterized by redistribution of adipose tissue, resulting in central fat deposition including dorsocervical (ie, "buffalo hump") or atrophy of subcutaneous adipose tissue including malar and temporal. Treatment for facial lipoatrophy includes use of fillers in the areas of subcutaneous deficiency; poly-l-lactic acid has been described as well as autologous fat transfer. Although nucleoside reverse transcriptase inhibitors can cause lipodystrophy, stopping the medication does not typically reverse the facial lipoatrophy. In addition, stopping HIV medications in general would not be advisable. While nutrition is important, parenteral nutrition would not reverse HIV-related lipodystrophy. Contouring with a parascapular free flap can sometimes be performed in cases of progressive facial hemiatrophy (Parry-Romberg syndrome), but this would be an excessive next step in management of HIV-associated facial lipodystrophy. Administration of botulinum toxin type A to the temporalis muscle can be used for temporal headaches. It would not help the soft-tissue atrophy found in this patient.

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Anesthetics 01-22, 24 Flashcards

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