Local Anesthetics Flashcards
A 36-year-old woman undergoes reduction mammaplasty. An intravenous infusion of vancomycin 1.5 g is started preoperatively as antibiotic prophylaxis. Medical history includes allergies to penicillin and clindamycin, but the patient has never received vancomycin. After 5 minutes of continuous infusion, an erythematous rash develops over the patient’s torso, neck, and face, and she reports headache and generalized pruritus. She remains hemodynamically stable and is otherwise asymptomatic. After discontinuing the antibiotic infusion, which of the following is the most appropriate next step in management?
A) Administer epinephrine intramuscularly
B) Administer morphine intravenously
C) Document the patients allergy to vancomycin in the medical record
D) Order a STAT vancomycin serum level
E) Resume the infusion at a slower rate once the patients symptoms improve
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.
2018
A 45-year-old man is brought to the emergency department after sustaining a gunshot wound to the chest. He is in respiratory distress and has decreased breath sounds on the right side. Needle decompression is performed in the right chest, and a tube thoracostomy is placed. The patient stabilizes. Which of the following initial findings is most likely in this patient?
A) Cardiac murmur
B) Decreased urine output
C) Hyperresonance of the left chest
D) Hypertension
E) Tracheal deviation to the left
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.
2018
A 30-year-old man comes to the emergency department 4 months after undergoing transplantation of the right hand because he has a painful, burning rash on the transplanted hand. Physical examination of the hand shows a maculopapular erythematous rash. Which of the following types of rejection is most likely in this patient?
A) Hyperacute
B) Accelerated
C) Acute
D) Chronic
E) Graft-versus-host
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.
2018
A 45-year-old man is brought to the emergency department/intensive care unit after sustaining multiple facial fractures and a closed head injury with intraparenchymal hemorrhage in a motor vehicle collision. He is currently intubated and unresponsive. Serum sodium concentration is 140 mEq/L. Which of the following is this patient’s free water deficit?
A) 0 L
B) 1 L
C) 2 L
D) 3 L
E) 4 L
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.
2018
Temporary paresthesia is most likely in which of the following teeth after an infraorbital nerve block is performed?
A) Both central incisors, ipsilateral lateral incisor and canine
B) Both central incisors, ipsilateral lateral incisor, canine, and first and second molars
C) Ipsilateral central incisor, lateral incisor, canine, and both bicuspids
D) Ipsilateral lateral incisor, canine, both bicuspids, and first and second molars
E) Ipsilateral canine, both bicuspids, and first and second molars
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.
2018
Which of the following patient positioning interventions is most appropriate for prevention of perioperative peripheral neuropathy?
A) Abducting the arms at 100 degrees in supine patients
B) Pronating the forearms in supine patients with arms tucked at side
C) Securing the arms in dorsal extension in supine patients
D) Stabilizing the neck in extended position in prone patients
E) Using leg holders with heel support in lithotomy position
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.
2018
A 28-year-old woman, gravida 2, para 1, is brought to the emergency department after a motor vehicle collision in which she was a restrained passenger. ATLS evaluation shows that her vital signs are stable, and she is calm and lucid. The patient reports that she is 32 weeks’ pregnant. Repeat blood pressure is 80/60 mmHg, and the patient reports that she feels light-headed; tachycardia is noted. After maintaining cervical spine precautions, which of the following is the most appropriate initial management of this patient?
A) Administer 2 L crystalloid bolus
B) Intubate the patient
C) Logroll the patient onto her left side
D) Place patient in Trendelenburg position
E) Transfuse 2 units of blood
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.
2018
A 42-year-old woman who is BRCA2-positive undergoes delayed reconstruction of both breasts with deep inferior epigastric artery perforator (DIEP) flaps. Medical history includes prophylactic mastectomy and failed implant reconstruction 3 months ago. After closure of the fascia of the rectus abdominis muscles, the triangle bounded by the latissimus dorsi, external oblique, and iliac crest is identified on each side. Infiltration of bupivacaine into which of the following planes is most likely to provide postoperative pain control of the abdominal flap donor site in this patient?
A) Between the external oblique and the internal oblique
B) Between the internal oblique and the transversus abdominis
C) Between the transversalis fascia and the peritoneum
D) Between the transversus abdominis and the transversalis fascia
E) In the deep subcutaneous tissues, superficial to the external oblique
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.
2018
A 32-year-old man, who is a football player, is brought to the emergency department after being found unconscious and facedown in his home. It is estimated that he was in that position for 6 hours. Physical examination shows swelling of the right forearm and hand. Which of the following physiologic abnormalities is most likely in this patient?
A) Hyperkalemia, hypercalcemia, metabolic acidosis
B) Hyperkalemia, hypocalcemia, metabolic acidosis
C) Hypokalemia, hypercalcemia, metabolic alkalosis
D) Hypokalemia, hypocalcemia, metabolic acidosis
E) Hypokalemia, hypocalcemia, metabolic alkalosis
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.
2018
A 56-year-old woman has been in the intensive care unit since she was struck by a car 2 weeks ago. She sustained multiple facial fractures, severe closed head injury with cerebral contusion, pelvic fractures, and multiple lower extremity fractures. The patient required emergent intubation and has been in a coma since the injury. The patient’s current serum sodium concentration is 148 mEq/L, and urinalysis demonstrates dilute urine with low osmolality. Neurogenic diabetes insipidus is suspected. A deficiency in which of the following hormones is most likely the principal cause of this electrolyte imbalance?
A) Aldosterone
B) Angiotensin
C) Cortisol
D) Renin
E) Vasopressin
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.
2018
An otherwise healthy 154-lb (70-kg) woman undergoes a planned facial aesthetic procedure using conscious sedation. The anesthetic plan includes a combination of intravenous 0.25 mg/kg midazolam and 12.5 mg/kg fentanyl. Midway through the procedure, two consecutive noninvasive blood pressure readings taken 5 minutes apart demonstrate a systolic blood pressure of 85 mmHg. Which of the following is the most appropriate next step in management of this patient’s hypotension?
A) Administer flumazenil
B) Administer naloxone
C) Administer a vasopressor intravenous bolus (ephedrine or phenylephrine)
D) Begin cardiopulmonary resuscitation
E) Increase intravenous fluids
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.
2018
A 60-year-old man is transferred to the surgical intensive care unit (SICU) following ventral hernia repair. Medical history includes coronary artery disease. Shortly after arrival in the SICU, the 12-lead ECG shown is obtained. This finding is most consistent with which of the following cardiac dysrhythmias?
A) Atrial fibrillation
B) Atrial flutter
C) First-degree AV block
D) Multifocal atrial tachycardia
E) Second-degree AV block
The correct response is Option E.
Cardiac dysrhythmias in the postoperative setting are extremely common, occurring 9% of the time in non-cardiac surgery patients without a history of cardiac disease to over 40% in cardiac surgery patients. In the surgical intensive care unit (SICU) setting, cardiac dysrhythmias may have several causes including hypoxia, cardiac ischemia, catecholamine excess, routine medications, and electrolyte abnormalities. It is important to be able to identify the characteristic electrocardiographic features of common dysrhythmias.
The PR interval is a measure of the conduction time through the AV node and bundle of His. When the PR interval is prolonged, the patient has a first-degree AV block. Second degree AV block occurs with intermittent failure of the conduction of the impulse to the ventricles. Progressive prolongation of the PR interval until a failure of conduction (“dropped” QRS complex) occurs is second degree AV block (Wenckebach block).
Multifocal atrial tachycardia is thought to be caused by abnormal automaticity. It demonstrates an irregular rate and rhythm, characterized by the presence of three or more morphologically different P waves on EKG with increased rates of 110 to 140 beats per minute.
Atrial fibrillation is one of the most common dysrhythmias encountered in an ICU setting. It is associated with dilation of the left atrium due to fluid shifts or structural heart disease. Echocardiographically, it is characterized by normal complex tachycardia without P waves.
Atrial flutter is associated with atrial enlargement and is caused by a reentrant circuit within atrial tissue. Increased atrial rates of 250 to 350 beats per minute are common, and not all of the atrial beats pass to the ventricle, typically in a 2:1 ratio. The EKG has a characteristic “sawtooth” flutter wave.
2018
Compared with the code team, which of the following is a typical criterion for calling the Rapid Response Team (RRT)?
A) Absence of respiratory effort
B) No recordable blood pressure
C) No recordable pulse
D) Rapid heart rate
E) Unresponsiveness
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.
2018
A 35-year-old woman is scheduled for abdominoplasty with flank liposuction. Regional anesthetic block is planned. The most appropriate location for placement of the anesthetic is between which of the following?
A) External oblique muscle and internal oblique muscle
B) Internal oblique muscle and transversus abdominis muscle
C) Skin and external oblique muscle
D) Transversalis fascia and peritoneum
E) Transversus abdominis muscle and transversalis fascia
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.
2017
A 42-year-old woman presents for fat grafting from the abdomen to the upper breast poles under intravenous sedation. Patient history includes implant-based breast reconstruction. She receives 1 g of intravenous cefazolin in the preoperative holding area. Ten minutes later, she has onset of generalized hives, flushing, and swelling of the lips. She reports dyspnea and has audible wheezing. The most appropriate next step is administration of epinephrine by which of the following routes?
A) Intradermal injection
B) Intramuscular injection
C) Intravenous bolus
D) Intravenous infusion
E) Subcutaneous injection
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.
2017
A 154-lb (70-kg), 42-year-old woman undergoes wide-awake flexor tendon repair during local anesthesia. The surgical area is infiltrated with a total of 20 mL of 1% lidocaine with epinephrine. To minimize bleeding, which of the following is the optimal timing between injection of the anesthetic and initiation of the incision?
A) 5 minutes
B) 10 minutes
C) 15 minutes
D) 25 minutes
E) 45 minutes
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.
2017
A 65-year-old woman is brought to the recovery room after undergoing brow lift surgery. Postoperatively, acute ST-elevation myocardial infarction is noted. Aspirin is administered. Frequent ventricular premature beats and occasional short runs of nonsustained ventricular tachycardia are noted on cardiac monitoring. Current blood pressure is 115/75 mmHg, heart rate is 65 bpm, and respiratory rate is 12/min. Oxygen saturation is 100%. Which of the following is the most appropriate next step in management?
A) Intravenous administration of amiodarone 150 mg over 10 minutes
B) Intravenous administration of flecainide 2 mg/kg body weight
C) Intravenous administration of lidocaine bolus 1 mg/kg body weight followed by continuous infusion at 1 mg/min
D) Replenishment of serum potassium to > 4.0 mEq/L and magnesium to > 2.0 mg/dL
E) Withhold administration of metoprolol
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.
2017
During surgical procedures that do not involve the airway, which of the following oxygen delivery methods is most likely to increase the risk of fire in the operating room?
A) Endobronchial tube
B) Endotracheal tube
C) Laryngeal mask
D) Nasal cannula
E) Tracheostomy tube with cuff
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.
2017
A 51-year-old woman undergoes bilateral breast reconstruction with free deep inferior epigastric artery perforator (DIEP) flaps. She is concerned about postoperative pain control. To achieve anesthetic effect, an infusion of 10 mL of 0.25% bupivacaine is administered bilaterally into the transversus abdominis plane (TAP) block space. Which of the following are the most appropriate anatomical landmarks to use when performing this technique?
A) Latissimus dorsi, external oblique, and iliac crest
B) Linea semilunaris, inferior epigastric vessels, and inguinal ligament
C) Quadratus lumborum, internal oblique, and 12th rib
D) Teres major, teres minor, and long head of the triceps
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.
2017
A 65-year-old man is evaluated for an increased serum potassium concentration of 6 mEq/L. ECG shows peaked T waves, decreased P wave amplitude, and prolonged QRS wave duration. Which of the following is the most appropriate initial step in management?
A) Administration of acetazolamide 250 mg intravenously
B) Administration of metoprolol succinate 20 mg in 4 mL nebulization, inhaled over 10 minutes
C) Administration of spironolactone 100 mg intravenously over 2 to 3 minutes, repeated after 5 minutes if ECG changes persist or recur
D) Administration of succinylcholine 30 g orally, and repeated every 2 hours as indicated
E) Administration of 10 units of regular insulin followed by 50 mL of 50% dextrose intravenously
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.
2017
An otherwise healthy 28-year-old woman undergoes emergency splenectomy because of isolated splenic rupture after sustaining blunt trauma. Examination shows hemodynamic instability. Postoperatively, the patient continues to experience hypotensive episodes that are difficult to manage. Total urine output is 200 mL over 12 hours. Tertiary survey identifies no ongoing hemorrhage or other injuries. Laboratory studies show:
Which of the following most closely represents the fractional excretion of sodium (FENa) in this patient?
A) 0.3%
B) 1.2%
C) 2.3%
D) 3.1%
E) 4.1%
The correct response is Option D.
Acute kidney injury (AKI, formerly called acute renal failure) is characterized by an abrupt decrease in renal function. The differential diagnosis can be categorized into prerenal, intrinsic renal, and postrenal causes. Of these, decreased renal perfusion (prerenal disease) and acute tubular necrosis (ATN) represent the two most common causes, accounting for 65 to 75% of all cases. The fractional excretion of sodium (FENa) has been shown in a variety of studies to more clearly differentiate between prerenal disease and ATN than other laboratory tests and guide patient management when taken in the context of history and physical examination. FENa measures the percent of filtered sodium and is calculated as:
FENa = [(UNa * PCr) / (PNa * UCr)]* 100%
where UNa and PNa represent urine and plasma concentrations of sodium, and UCr and PCr represent and urine and plasma concentrations of creatinine, respectively.
In general, a FENa below 1% suggests prerenal disease, where there is appropriate reabsorption of the majority of all filtered sodium in response to decreased renal perfusion. FENa above 2% reflects inappropriate salt wasting indicative of ATN. Of note, important limitations of the predictive value of a high FENa include diuretic therapy and chronic renal failure, by altering normal salt handling.
In the example given above, FENa = [(35 * 4.5) / (145 * 35)] * 100% = 3.1%
2017
A 28-year-old woman is scheduled to undergo office-based outpatient augmentation mammaplasty during general anesthesia. Medical history includes postoperative nausea and vomiting, and motion sickness. In addition to ondansetron 4 mg intravenously, preinduction administration of which of the following drugs is likely to be most effective in this patient?
A) Aprepitant 40 mg orally
B) Diphenhydramine 25 mg intravenously
C) Droperidol 1.25 mg intravenously
D) Metoclopramide 25 mg intravenously
E) Promethazine 25 mg orally
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.
2017
A 42-lb (19-kg), 5-year-old girl is brought to the emergency department because of multiple lacerations of the face after being bitten by a dog. Intravenous sedation is administered by the emergency room physician. The plastic surgeon initiates repair of the lacerations by infiltrating an infusion of 60 mL of 0.5% lidocaine with 1:200,000 epinephrine. Ten minutes after the procedure begins, the patient begins to have a seizure. Pulse oximetry and vital signs are within normal range. Which of the following is the most appropriate next step in management?
A) Administer epinephrine
B) Administer propofol
C) Initiate lipid emulsion therapy
D) Secure the airway and ventilate with oxygen
E) Transfer the patient to the PICU
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.
2017
A 50-year-old woman is scheduled to undergo bilateral deep inferior epigastric artery perforator (DIEP) flap breast reconstruction. A donor site regional block with liposomal bupivacaine is planned for analgesia. Which of the following injection locations is most likely to improve pain control and decrease narcotic use in this patient?
A) Between external oblique and internal oblique fascias
B) Between internal oblique and transversus abdominis fascias
C) Deep to rectus abdominis fascia
D) Deep to transversus abdominis fascia
E) Subcutaneous plane
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.
2016
A healthy 154-lb (70-kg), 30-year-old woman is undergoing liposuction of multiple sites. Five minutes after the local anesthetic infusion, she sustains a cardiac arrest. Local anesthetic systemic toxicity is diagnosed. After CPR is initiated, administration of which of the following is the most appropriate next step in management?
A) Adenosine
B) Intralipid
C) Propranolol
D) Vasopressin
E) Verapamil
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.
2016
A 55-year-old woman is evaluated for an incisional hernia that developed after a complicated right hemicolectomy 5 years ago. Medical history includes hypertension. BMI is 34 kg/m2. She reports shortness of breath when trying to scrub floors at work but is able to climb a flight of stairs or walk up a hill without symptoms. There are no other respiratory or cardiovascular issues. Cardiovascular examination shows no abnormalities. Recent electrocardiography, complete blood count, and basic metabolic panel show no abnormalities. Hernia repair with separation of components is being considered. Which of the following is the most appropriate next step in the preoperative cardiac assessment of this patient?
A) Cardiac catheterization
B) Echocardiographic exercise stress testing
C) Echocardiography at rest
D) Nuclear cardiac pharmacologic stress testing
E) No further cardiac testing is needed
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.
2016
A 65-year-old woman is scheduled to undergo unilateral breast reconstruction with tissue expander. Medical history includes placement of a drug-eluting stent 4 months ago. Current medications include aspirin and clopidogrel. The surgical oncologist does not want to wait longer to perform the mastectomy. Which of the following is the most appropriate management of preoperative medications in this patient?
A) Continue both aspirin and clopidogrel
B) Discontinue aspirin and continue clopidogrel
C) Discontinue both aspirin and clopidogrel
D) Discontinue both aspirin and clopidogrel; start prophylactic enoxaparin
E) Discontinue clopidogrel and continue aspirin
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.
2016
A critically ill 69-year-old man is observed to have new-onset atrial fibrillation complicated by rapid ventricular response. Angina and hemodynamic instability with hypotension and acute ST depression is noted. Which of the following is the next step in management?
A) Emergency cardiac catherization with AV nodal ablation followed by permanent ventricular pacing
B) Heparin anticoagulation and emergency transesophageal echocardiography (TEE) to rule out left atrial thrombus
C) Immediate external electrical cardioversion
D) Intravenous administration of amiodarone with loading dose and titrated infusion until sinus rhythm is restored
E) Intravenous administration of a beta blocker or nondihydropyridine calcium channel blocker to slow the ventricular heart rate
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.
2016
A 42-year-old woman is scheduled to undergo reduction mammaplasty. Medical history includes macromastia and von Willebrand disease. Preoperatively, administration of desmopressin (DDAVP) is planned for bleeding prophylaxis. The total preoperative dose is best determined by measuring the activity levels of vWF:RCoF (von Willebrand factor ristocetin cofactor) and which of the following coagulation factors?
A) II
B) V
C) VII
D) VIII
E) X
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.
2016
A 55-year-old woman is evaluated for mild cellulitis after undergoing cosmetic excision of a facial mole 7 days ago. Cephalexin is prescribed. Approximately 30 minutes after taking her first dose, she returns to the office because of sudden and progressive onset of generalized hives, periorbital edema, and flushing. The patient appears confused and then collapses. Blood pressure is 85/50 mmHg. An audible wheeze is noted. Which of the following is the most appropriate next step in management?
A) Administration of albuterol nebulizer
B) Administration of diphenhydramine and ranitidine intravenously
C) Injection of epinephrine (1 mg/mL) 0.3 to 0.5 mg intramuscularly
D) Injection of methylprednisolone 125 mg intramuscularly
E) Rapid infusion of 0.9% saline 1 to 2 L intravenously
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.
2016
A critically ill 65-year-old woman is brought to the intensive care unit, where she sustains respiratory arrest. Temperature is 101.3ºF (38.5ºC), heart rate is 105 bpm, and blood pressure is 85/60 mmHg. Hematocrit is 35%. She is immediately intubated. Noninvasive pulse oximetry is initiated to monitor oxygen saturation (SaO2). Which of the following conditions is most likely to alter pulse oximetry values in this patient?
A) Anemia
B) Fever
C) Hypotension
D) Tachycardia
E) Tachypnea
The correct response is Option C.
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.
2016
A 63-year-old man with end-stage renal failure is evaluated for unilateral leg swelling and shortness of breath 2 days after undergoing bilateral axillary hidradenitis excision. Current medication includes aspirin. Oxygen saturation on room air is 88%. During diagnostic evaluation, empiric administration of which of the following drugs is most appropriate?
A) Intravenous heparin
B) Oral clopidogrel
C) Oral rivaroxaban
D) Oral warfarin
E) Subcutaneous enoxaparin
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.
2016
A 69-year-old man is evaluated in the intensive care unit 5 days after undergoing abdominal wall reconstruction for a multiple-recurrence ventral hernia. Medical history shows no cardiac disease. Temperature is 103°F (39°C), heart rate is 110 bpm, and mean arterial pressure (MAP) is 50 mmHg. Airway and ventilation are secured, and supplemental oxygen is initiated. Hemoglobin concentration is 9 g/dL. Which of the following is the most appropriate next step in management?
A) Initiation of inotropic support
B) Initiation of vasopressor support
C) Introduction of a pulmonary artery catheter to monitor wedge pressures
D) Volume resuscitation with crystalloid
E) Volume resuscitation with packed red blood cells
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.
2016
A 5-year-old boy is brought to the emergency department 45 minutes after accidentally injecting his palm with epinephrine from an auto-injector (EpiPen). On physical examination, the ring finger is soft and pale, and capillary refill time is poor. A small puncture mark is noted on the flexor surface of the palm just proximal to the metacarpophalangeal (MCP) joint. Which of the following is the most appropriate next step in management?
A) Application of a hot pack
B) Emergent operative exploration
C) Subcutaneous injection of nifedipine
D) Topical nitroglycerin paste
E) Observation
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.
2015
A 35-year-old man undergoes a 90-minute rhytidectomy procedure with intravenous sedation. The patient smokes 10 cigarettes daily, but is otherwise healthy. Which of the following factors most likely places this patient at increased risk for postoperative nausea and vomiting?
A) Duration of procedure
B) Gender
C) History of cigarette smoking
D) History of postoperative nausea and vomiting
E) Type of anesthesia
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.
2015
A 37-year-old man, who is American Society of Anesthesiologists (ASA) Class 2, comes to the office for evaluation and treatment of human immunodeficiency virus (HIV)–associated lipodystrophy. The patient has a CD4 count of 100 cells/mm3. Autologous fat grafting is planned. Which of the following factors is most likely to increase this patient’s risk of postoperative complications?
A) ASA Class
B) CD4 cell count
C) HIV seropositivity
D) Percutaneous surgery
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.
2015
A 35-year-old woman comes to the office for consultation on augmentation mammaplasty. During preoperative workup, she reports that her mother has a history of malignant hyperthermia. The patient has never undergone surgery. Which of the following anesthetic agents is most appropriate for this surgery?
A) Desflurane
B) Halothane
C) Isoflurane
D) Propofol
E) Succinylcholine
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.
2015
A 42-year-old woman, with a history of anaphylactic reaction to procaine, comes to the office for consultation regarding augmentation mammaplasty. Anesthetics that contain which of the following should be avoided in this patient?
A) Acetaldehyde
B) Epinephrine
C) Iodine
D) Methylparaben
E) Para-aminobenzoic acid
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.
2015
An otherwise healthy 52-year-old woman with a family history of cardiac disease undergoes suction-assisted lipectomy of the flanks, thighs, and abdomen using a tumescent technique. She returns to the emergency department 6 hours after discharge because of slurred speech and restlessness. Which of the following is the most likely diagnosis?
A) Fat embolism
B) Lidocaine toxicity
C) Parietal stroke
D) Pulmonary embolism
E) Third spacing
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.
2015
A 40-year-old woman with a history of severe postoperative nausea and vomiting is scheduled for exchange of bilateral breast tissue expanders for permanent silicone implants. Use of which of the following medications is most likely to decrease the chance of postoperative nausea?
A) Bupivacaine
B) Fentanyl
C) Isoflurane
D) Midazolam
E) Nitrous oxide
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
2014
A 54-year-old woman has onset of ventricular fibrillation and severe hypotension 5 minutes after 30 mL bupivacaine 0.5% is administered to the ankle for postoperative pain control during reconstruction of the foot. After initiation of cardiopulmonary resuscitation, intravenous administration of which of the following is the most appropriate management?
A) Atropine
B) Dantrolene
C) Flumazenil
D) Lipid emulsion
E) Metoprolol
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.
2014
A 16-year-old boy who has asthma is brought to the emergency department 3 hours after accidentally injecting the index finger of the nondominant hand with his epinephrine auto-injector. On examination, the finger is cool, pale, and painful. Which of the following drugs works to competitively antagonize the sympathomimetic effects of epinephrine?
A) Lidocaine
B) Marcaine
C) Nitroglycerin paste
D) Phentolamine
E) Prostacyclin
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.
2014
A 53-year-old woman comes to the office for removal of multiple nevi. On injection of lidocaine, which of the following signs and symptoms is most likely to suggest lidocaine toxicity in this patient?
A) Bronchospasm
B) Hypertension
C) Tachycardia
D) Tinnitus
E) Urticaria
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.
2014
A 37-year-old woman is scheduled to undergo skin-sparing mastectomy of the left breast with immediate deep inferior epigastric perforator (DIEP) flap reconstruction. Which of the following interventions is most likely to decrease this patient’s postoperative narcotic needs?
A) Application of a preoperative compression garment
B) Hypnosis
C) Ondansetron therapy
D) Oxycodone therapy
E) Pregabalin therapy
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.
2019
A 65-year-old woman remains intubated in the intensive care unit after undergoing a prolonged operation. Arterial blood gas analysis shows respiratory acidosis. An increase in respiratory minute ventilation is planned. Minute ventilation is calculated by multiplying the respiratory rate and which of the following parameters?
A) Inspiratory capacity
B) Residual volume
C) Tidal volume
D) Total lung capacity
E) Vital capacity
The correct response is Option C.
Minute ventilation is calculated by multiplying respiratory rate and tidal volume. Tidal volume is the amount of air/gas displaced during each quiet breath, using no extra inspiratory (“deep breath”) or expiratory effort.
Minute ventilation is an important concept in mechanical ventilation because of its inverse relationship with blood carbon dioxide levels. The caveat of this relationship is that not all inhaled air/gas takes part in gas exchange, whether because it remains in the conductive airways (ventilator tubing, endotracheal tube, trachea, etc) or it reaches alveoli that are not adequately perfused. The volume of air/gas that does not take part in gas exchange is called dead space.
Residual volume is the volume of air still remaining in the lungs after the most forcible expiration possible.
Inspiratory capacity is the volume of air that enters the lungs during the most forcible inspiration possible, starting at rest. Inspiratory reserve volume equals inspiratory capacity minus tidal volume, or the difference between the deepest breath and a quiet breath.
Expiratory reserve volume is the amount of air that can still be expired after a quiet expiration ends. It requires contraction of expiratory chest wall muscles, as opposed to quiet expiration, which is passive.
Vital capacity is the total amount of air that can be forcefully expired from the lungs after the most forcible inspiration possible. It represents the addition of inspiratory reserve, tidal, and expiratory reserve volumes.
Total lung capacity is the combination of vital capacity and residual volume.
2019
A 48-year-old man who sustained severe traumatic brain injury and extensive facial fractures in a motor vehicle collision 2 weeks ago is receiving ventilatory support and enteral nutrition via feeding tube. An indirect calorimetry assessment shows a respiratory quotient (RQ) value of 1.3. This value is most closely associated with which of the following types of metabolism?
A) Carbohydrate oxidation
B) Ketosis
C) Lipid oxidation
D) Lipogenesis
E) Protein oxidation
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.
2020
A 71-year-old man with chronic obstructive pulmonary disease (COPD) is transferred to the hospital with multiple facial lacerations and fractures following a fall. He has increasing confusion on arrival at the hospital. His wife mentions that he had bled a significant amount after the fall. Laboratory studies show:
On the basis of these findings, this patient’s primary metabolic disorder is which of the following?
A) Metabolic acidosis due to exacerbation of his COPD
B) Metabolic acidosis due to hemodilution from bleeding
C) Metabolic alkalosis due to exacerbation of his COPD
D) Metabolic alkalosis due to hemodilution from bleeding
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.
2021
A 61-year-old woman presents to discuss oncoplastic reduction mammaplasty. Medical history includes a femur fracture sustained during a fall 4 months ago. Recovery was complicated by a pulmonary embolus. Current medications include warfarin therapy. Her hematologist has recommended bridging therapy to prevent recurrent embolus. Which of the following is the most appropriate regimen to bridge anticoagulation with low-molecular weight heparin (LMWH) in this patient?
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.
2022
A 42-year-old woman undergoes deep inferior epigastric artery perforator flap breast reconstruction. An ultrasound-guided transversus abdominis plane regional block with liposomal bupivacaine is planned. The ultrasound probe is placed directly over the abdominal wall musculature in the anterior axillary line. The sonographic image is shown. Injection at which of the following levels is most appropriate?
The correct response is Option C.
Transversus abdominis plane regional anesthetic blocks have been shown to decrease narcotic consumption and abdominal pain following abdominal-based microsurgical breast reconstruction. The sensory nerves to the anterior abdominal wall run in the interfascial plane between the internal oblique and transversus abdominis muscles. A successful regional block depends on precise identification of the proper plane for the injection. The arrow indicated by letter C represents the transversus abdominis plane.
The arrow indicated by letter A indicates the interfascial plane between the internal and external oblique muscles.
The arrow indicated by letter B indicates the body of the internal oblique muscle.
The arrow indicated by letter D indicates the peritoneum.
The arrow indicated by letter E indicates the contents of the abdominal cavity.
2022
A 43-year-old woman is scheduled to undergo bilateral tissue expander-based breast reconstruction. Preoperative pectoral nerve 1 and 2 blocks with liposomal bupivacaine with ultrasound guidance is performed. An image is shown. When performing pectoral nerve 1 block in this patient, which of the following is the most appropriate location for infiltration of the local anesthetic?
A) Between the breast parenchyma and pectoralis major
B) Between the pectoralis major and pectoralis minor
C) Between the pectoralis minor and the serratus anterior
D) Between the serratus anterior and the latissimus dorsi
The correct response is Option B.
The pectoral nerve (PECS) 1 and 2 anesthetic blocks have become increasingly common methods for regional anesthesia to decrease postoperative pain in many early recovery after surgery (ERAS) protocols. The PECS blocks are thoracic regional fascial plane blocks that typically require ultrasound guidance for proper infiltration of the anesthetic between the muscles of the thoracic wall.
A PECS 1 block is performed between the pectoralis major and pectoralis minor muscles and anesthetizes the lateral and medial pectoral nerves. A PECS 2 block, in addition to the PECS 1 block, involves an additional injection of anesthetic between the pectoralis minor and serratus anterior muscles and blocks the intercostal and intercostobrachial nerves. The serratus plane block is another thoracic regional fascial plane block requiring injection of local anesthetic between the serratus anterior and latissimus dorsi muscles in order to block the long thoracic and thoracodorsal nerves.
2022
