Anesthesia and pain control questions OMSITE Flashcards

Question

An 18 year-old with Cerebral Palsy (CP) requires intubation for a general anesthetic. Succinylcholine is contraindicated in this patient secondary to A. structural similarity to acetylcholine. B. potential for a significant increase in circulating levels of potassium. C. deficiency of pseudocholinesterase. D. fasciculation and post-operative muscle pain.

Answer 1

Answer: B Rationale: Circulating potassium increases significantly in patients with CP following administration of succinylcholine and may lead to lethal arrhythmias. Reference: Firestone, Lebowitz and Cook: Clinical Anesthesia Procedures of the Massachusetts General Hospital , Third edition, P. 171 Barash, Cullen and Stoelting, Handbook of Clinical Anesthesia, Fourth edition, P.585

Answer 2

Answer: A Rationale: Parkinson's disease, myasthenia gravis, a transection of the vertebral column above T4, and diabetes mellitus all increase the risk of aspiration. Parkinson's disease and myasthenia gravis impair the patient's ability to control their airway. Parkinson’s' disease is a neurodegenerative disease characterized by a loss of dopaminergic neurons in the substantia nigra of the basal ganglia. Clinical signs and symptoms include a resting tremor, rigidity, postural instability and bradykinesia. Myasthenia gravis is an autoimmune disease of the neuromuscular junction. Clinical symptoms include fatigue, weakness of the striated muscles, diplopia, inspiratory muscle weakness, and bulbar weakness with impaired ability to handle secretions and swallow. The diabetic patient may have autonomic dysfunction resulting in gastroparesis. Frequently gastroparesis is undiagnosed and asymptomatic. This increases the risk of gastric aspiration. The patient with systemic lupus erythematosus may present anesthetic airway and pulmonary concerns such as reduced TMJ range of motion, decreased arytenoid movement, diaphragmatic dysfunction, pulmonary infiltrates and reduced PFTs. However, the patient is not at increased risk for aspiration. Reference: Altee John L. Complications in Anesthesia. WB Saunders 1999 Roizen MF, Fleisher LA. Essence of Anesthesia Practice. WB Saunders 1997

Answer 3

Answer: D Rationale: Myasthenia gravis (MG) is a neuromuscular disease that is characterized by weakness and fatigability of skeletal muscles. The MG patient is more sensitive to the use of nondepolarizing relaxants. However, because there are fewer functional receptors the MG patient may demonstrate increased resistance to depolarizing muscular relaxants. While many anesthesiologists may prefer to avoid neuromuscular blocking agents, succinylcholine (in higher doses) can be used in the MG patient and provide satisfactory intubating conditions. Succinylcholine may precipitate hyperkalemia in muscular dystrophy, spinal cord injuries less than 6 to 8 months and MS. Reference: Altee John L. Complications in Anesthesia. WB Saunders 1999 Roizen MF, Fleisher LA. Essence of Anesthesia Practice. WB Saunders 1997

Answer 4

Answer: D Rationale: No treatment is required for a normal FEV1/FVC. Reference: Firestone, Lebowitz and Cook: Clinical Anesthesia Procedures of the Massachusetts General Hospital , Third edition, P. 35-7 Barash, Cullen and Stoelting, Handbook of Clinical Anesthesia, Fourth edition, P. 419-22

Answer 5

Answer: C Rationale: Metoclopramide would increase gastric emptying and increase esophageal sphincter tone. This would help decrease the risk of aspiration. All the other choices decrease esophageal sphincter tone and would increase the risk of aspiration. Reference: Firestone, Lebowitz and Cook: Clinical Anesthesia Procedures of the Massachusetts General Hospital , Third edition, P. 624-5 Barash, Cullen and Stoelting, Handbook of Clinical Anesthesia, Fourth edition, P. 549

Answer 6

Answer: B Rationale: The laryngeal mask airway is an airway device that is placed in the hypopharynx above the opening of the larynx. The LMA does not protect against aspiration of stomach contents and insufflation of the stomach can be expected with pressures above 20 cm of water. The black orientation line faces cephalad when in correct position. Delivery of emergency drugs through a LMA are less successful (approximately 20% successful administration) than via an endotracheal tube. All sizes of the LMA have a cuff that allows for seating of the LMA in the hypopharynx. Reference: The LMA Manual. The Laryngeal Mask Airway Company, LTD. Todd DW. Use of the LMA for Outpatient General Anesthetics, Pro. J Oral and Maxillofac Surg, 61:2003.

Answer 7

Answer: D Rationale: It is likely that this child has an upper respiratory infection (URI). Signs of an URI include fever, fatigue, loss of appetite, productive cough, and thick nasal discharge. Children with URI have an irritable airway and are at increased risk for laryngospasm, bronchospasm, postintubation croup, pneumonia, and episodes of desaturation. Bronchial hyperreactivity may last 4 to 6 weeks after an URI; it is recommended to delay treatment for at least 6 weeks. If urgent or emergency surgery is necessary a LMA may reduce complications associated with an irritable airway. Reference: Cote, Charles J., Pediatric Anesthesia, pg. 2381 - 2382 in Miller's Anesthesia, Sixth Edition, Volume 2, by Elsevier Inc. Dembo, Jeffrey B., Pediatric Consideration in Office Anesthesia, pg. 108, OMS Knowledge Update, Vol. 1, Part 1, August 1994

Answer 8

``` Answer: A Rationale: Mechanical ventilation may be either volume or pressure controlled. Volume controlled ventilation consists of CMV(controlled mechanical ventilation), ACV (assist controlled ventilation), IMV (intermittent controlled ventilation), SIMV (synchronized intermittent controlled ventilation). Pressure controlled ventilation is either PSV (pressure support ventilation) which is patient triggered or PCV (pressure controlled ventilation) which is ventilator triggered. CMV is most commonly used during general anesthesia in the neuromuscularly blocked patient. The various other settings can be used for ventilatory support and weaning. The ACV mode requires that the patient trigger a breath. When the patient triggers a breath the ventilator delivers a preset volume. The disadvantage of the mode is that if the patient is tachypneic excessive volume and thus a respiratory alkalosis will develop. Alternatively, IMV allows the patient to breath spontaneously and delivers positive pressure ventilation at a preset volume and rate to ensure oxygenation and ventilation. SIMV prevents PVP (positive pressure ventilation) during a spontaneous breath. Reference: Miller, Stoelting, Basics in Anaesthesia ```

Answer 9

Answer: C Rationale: The principal hemodynamic goals of managing patients with mitral stenosis are to maintain a slower to normal sinus rhythm and to avoid tachycardia, large increases in cardiac output, and both hypovolemia and fluid overload by judicious fluid therapy. Reference: DE Longnecker, FL Murphy, Introduction to Anesthesia, 9th ed., pp. 290, Saunders, 1997 GE Morgan et al, Clinical Anesthesiology, pp. 411, Lange/McGraw-Hill, 2002

Answer 10

Answer: A Rationale: The symptoms are classic for acute intermittent porphyria, an autosomal dominant condition leading to a deficiency in uroporphyrinogen synthetase activity, causing an accumulation of uroporphobilogen, which is excreted in the urine turning it a dark color. Classic symptoms of an acute attack include intense abdominal pain, motor weakness, (usually starting proximally in the upper limbs) and confusion/agitation. These are due to nervous system dysfunction and demylenization. Diagnosis is by family history, increased levels of urinary porphobilogen, and deficient uroporphyrogen synthetase in the red blood cells. Treatment for an acute episode is supportive, including withdrawal of precipitating agents, carbohydrate support, hydration, and careful administration of hematin. Many agents have been implemented as potential triggering agents for acute intermittent porphyria. The most commonly cited are barbiturates. Morphine, fentanyl and its conjoiners, and nitrous oxide are considered safe. Other anesthetic agents implicated as causative or exacerbative agents for AIP include most potent inhalation volatile anesthetics, benzodiazepines, ketamine, etomidate, meperidine, and lidocaine. Reference: Weinberg GL (ed;): Basic Science Review of Anesthesiology, McGraw-Hill, New York, 1997 pp64-66 Benumof JL (ed.) Anesthesia and Uncommon Diseases, WB Saunders, Philadelphia, 1998 pp 162-163

Answer 11

Answer: C Rationale: Postextubation stridor is a result of laryngeal inflammation reducing the airway DIMENSION. In a young child it may be secondary to irritation of the endotracheal tube infringing on the narrowest part of the child's airway – being the cricoid cartilage. Maneuvers to avoid such include using a cuffless tube and ensuring that there is an air leak around the tube. Movement of the patient's head during surgery can cause a displacement of the tube superiorly (essentially extubating the patient) or inferiorly (irritating the mucosa around the region of the cricoid cartilage). The risk of the child developing postextubation stridor persists for up to 24 hours after the extubation. Aerosolized 2.25% racemic epinephrine produces mucosal vasoconstriction and reduces laryngeal edema. The patient has a history of asthma and could have developed a bronchospastic event post- operatively. However, the clinic presentation was an inspiratory sound where bronchospasm would more likely demonstrate an expiratory wheeze. Laryngospasm is also a possibility but there is nothing in the history to put the patient at risk for a laryngospasm 30 minutes postextubation and it should not be highest on your differential. Reference: Altee John L. Complications in Anesthesia. WB Saunders 1999 Roizen MF, Fleisher LA. Essence of Anesthesia Practice. WB Saunders 1997

Answer 12

Answer: C Rationale: Intraoperative bronchospasm should be first treated by confirming that there is no mechanical obstruction of the tracheal tube, tube placement is correct and adequate depth of anesthesia is present. The initial treatment consists of the administration of a -agonist such as albuterol. Epinephrine should be reserved for a severe bronchospasm refractory to initial -agonist therapy because of the potential for severe adverse effects. Steroids are not helpful in the acute management and muscle paralysis will not improve the situation. Differential diagnosis should also include pneumothorax, pulmonary edema, pulmonary embolus, and pulmonary aspiration. Reference: Stoelting RK, Dierdorf SF. Anesthesia and Co-Existing Disease, Churchill Livingstone, 2002. AAOMS Office Emergency Manual, AAOMS, Chicago 2004.

Answer 13

Answer: B Rationale: In infants or young children, the narrowest portion of the larynx is at the cricoid cartilage. In a child, an endotracheal tube might pass easily through the vocal cords but not through the subglottic region. The cricoid is the only complete ring of cartilage in the laryngotracheobronchial tree and is therefore nonexepandable. A tight fitting endotracheal tube that compresses the tracheal mucosa at this level may cause edema and result in increased airway resistance at the time of extubation. For this reason, uncuffed endotracheal tubes are usually preferred for infants or young children. As the child matures (age 10 to 12 years of age), the cricoid and thyroid cartilages have grown, eliminating the narrowing of the subglottic area and angulation of the vocal cords. Reference: Cote, Charles J., Pediatric Anesthesia, pg. 2376 in Miller's Anesthesia, Sixth Edition, Volume 2, by Elsevier Inc.

Answer 14

Answer: B Rationale: Etiologic treatment of an MH episode requires dantrolene at an initial dose of 2-3 mg/kg. Cardiac dysrrhythmias should be treated by procainamide at an initial dose of 100mg IV. Management of hyperkalemia to correct the arrhythmia can be achieved with regular insulin 10 units IV together with 1 amp of D50, as well as sodium bicarbonate to help drive potassium intracellularly. Calcium channel blockers such as cardizem are contraindicated because they can cause severe myocardial depression in the presence of dantrolene. Reference: MHAUS, Emergency Therapy for MH Crisis Stoelting RK, Dierdorf SF. Anesthesia and Coexisting Disease, Churchill- Livingston, 2002.

Answer 15

ANSWER: D RATIONALE: Although many thiobarbiturates decrease cerebral metabolism and electrical activity and are used as anticonvulsants, the oxybarbiturate methohexital has increased central nervous system excitatory effects and may precipitate seizures in epileptics. Propofol, fentanyl, and ketamine have no such pro-convulsant effects.

Answer 16

ANSWER: C RATIONALE: This situation may appear to be pulmonary in origin, but in fact represents acquired methemoglobinemia. This condition can be precipitated by nitrates, (such as isosorbide dinitrate) acetaminophen, prilocaine, articaine, and a number of other medications, especially in genetically susceptible individuals. The oxidized (ferric) state of the methemoglobin molecule cannot be reversed by increasing the FIO2, which also may decrease the respiratory drive in COPD. Sedation reversal by flumazenil will have no effect on the condition. Cautious administration of methylene blue will reduce methemoglobin back to a ferrous state, normalizing the oxygen binding/delivering capacity of hemoglobin.

Answer 17

ANSWER: C RATIONALE: Vecuronium, a non-depolarizing muscle relaxant, is a steroidal medication and therefore lacks histamine-releasing tendencies that occur with the benzoisoquinolone non- depolarizers. Histamine release can increase tracheobronchial mucosal edema and cause bronchoconstriction. Desflurane, although a potent bronchodilator, is also an airway irritant, causing coughing and increasing sympathetic tone; and may not be desirable in the patient with chronic bronchitis. Methohexital when used as an induction agent can precipitate laryngospasm and bronchospasm in airways already irritated by chronic disease. Nitrous oxide's extremely low blood solubility will cause it to come out of solution to expand areas of hypoventilation in the lung, which may cause pneumothorax in patients with emphysematous changes and pulmonary blebs.

Answer 18

ANSWER: B RATIONALE: Acute respiratory failure is the inability of the lungs to provide adequate arterial oxygenation with or without acceptable elimination of carbon dioxide. It culminates in hypoventilation, hypercarbia, and hypoxemia. Partial obstruction of the airway at the level of the trachea represents stridor. Measurement of arterial blood gases and pH are mandatory in the diagnosis and management of acute respiratory failure. It is distinguished from chronic respiratory failure on the basis of the relationship of the PaCO2 to pH (acute respiratory failure shows no partial compensation of hypercarbia.) Respiratory failure is diagnosed with arterial hypoxemia (PaO2 50mm Hg), and SaO2

Answer 19

Answer: A Rationale: The respiratory apparatus and physiology in children differs from adults in many ways. Children have a high metabolic rate, thus a high oxygen demand and hypoxemia develops rapidly their upper airway has a smaller caliber, large soft tissues, larynx that is positioned cephalad, with a shorter trachea, and epiglottis that is short and narrow. This results in increased airway resistance, easy obstruction, difficult intubation, easy extubation. The child's ribs and sternum are compliant, and when respiratory efforts are diminished, their reserve decreases. The child relies more on diaphragatic breathing, therefore high intrathoracic pressure or abdominal distention diminishes ventilation. The child possesses low lung compliance and therefore ventilation is inefficient during respiratory distress. Reference: American College of Surgeons Committee on Trauma:ATLS Advanced Trauma Life Support Program for Doctors. 7th Edition, American College of Surgeons, Chicago, IL, 2004, pgs 243-262.

Answer 20

Answer: D Rationale: Intubation of an awake patient causes significant airway stimulation and irritation. Anesthetizing the mucosa of the upper airway can improve comfort and lessen unpleasant stimulation associated with this procedure. Topical application of local anesthetic agent can be accomplished orally (as a swish and swallow) or by transtracheal deposition into the tracheal lumen. However, these techniques may blunt the glottic and cough reflex, increasing the patient's susceptibility to aspiration. The gag reflex can be further controlled by supplementary nerve blocks to the lingual branch of the glossopharyngeal nerve and the superior laryngeal nerve. The glossopharyngeal nerve block requires the bilateral deposition of local anesthetic agent into the caudad portion of the tonsillar pillar. The superior laryngeal nerve block is accomplished by deposition of local anesthetic agent into the thyrohyoid membrane.

Answer 21

Answer C Rationale: Propofol can produce bronchodilation and decrease the incidence of intraoperative wheezing in patients with asthma. In one study comparing propofol, methohexital and thiopental propofol demonstrated a significantly decreased incidence of wheezing after induction and intubation compared to the other agents. Etomidate has less of a depressant effect on ventilation compared to barbiturates, however, but is not protective against bronchospasm.

Answer 22

Answer: D Rationale: Most anesthetics depress the hypercapneic and hypoxic respiratory drive, diminish upper airway tone, blunt upper airway reflexes and decrease functional residual capacity. While the respiratory drive may be blunted and the reflexes diminished the anesthetic doses administered to this size patient will allow continual spontaneous ventilation if the airway is kept patent either with positioning (e.g. chin – forehead lift) or airway devices (e.g. nasopharyngeal airway). This patient is making ventilatory efforts. The respiratory noises are most likely associated with supraglottic obstruction. Alleviating the obstruction should facilitate ventilation and increase oxygen saturation. The increase in heart rate is most likely secondary to the methohexital.

Answer 23

Answer: C Rationale: There are a number of factors that can contribute to a patient's disorientation or combativeness after an anesthetic. Combativeness may be manifest as the patient emerges from a general anesthetic until oriented. The surgeon must always consider that the patient is hypoxic. Tertiary anticholinenergic drugs (atropine and scopolamine) can cross the blood brain barrier and lead to postoperative delirium. Glycopyrrolate is a quarternary agent and does not cross the blood brain barrier. Propofol is associated with rapid recovery and euphoria. Long acting benzodiazpines may also contribute to disorientation on emergence. In young healthy patients recovery from midazolam is generally not associated with disorientation. Meperidine, although rare, because of its atropine-like structure can cause post-operative agitation and combativeness.

Answer 24

Answer: A Rationale: Serotonin, dopamine, acetylcholine and histamine receptors are located in the chemoreceptor trigger zone. All of the above agents act to some degree on the dopamine receptor. Of these agents, compazine achieves its effect by strongly binding to the receptor. Scopolamine and diphenhydramine bind only weakly.

Answer 25

Answer: B Rationale: Tricylcic antidepressants (elavil) prevent the reuptake of catecholamines. Ketamine has sympathomimetic effects and will be associated with an increase in heart rate and blood pressure. These effects will be potentiated by the tricyclic antidepressant and compounded by the patient's history of hypertension. Methohexital is not contraindicated in a patient with controlled asthma.

Answer 26

Answer: B Rationale: Ketamine is associated with an increase in salivation. An anticholinergic agent is frequently combined with ketamine to decrease the hypersalivation. Intramuscularly administered glycopyrrolate has a peak effect in approximately 30 minutes, while intravenously administered glycopyrrolate has a peak effect in approximately 1 minute. Robinal is a quaternary amine and does not cross the blood brain barrier compared to atropine, which is a tertiary amine and does cross the blood brain barrier. However, the incidence of emergence phenomenon is not higher with atropine when compared to glycopyrrolate. Ketamine has sympathomimetic effects resulting in an increase in heart rate. Atropine has a greater potential to potentiate the tachycardia associated with ketamine.

Answer 27

Answer: B Rationale: Ketamine has sympathomimetic effects and causes prominent changes in heart rate, cardiac index, and systemic vascular resistance. These changes cause an increase in myocardial oxygen consumption that may be detrimental to the patient with CAD.

Answer 28

Answer: B Rationale: Most anesthetics depress the hypercapneic and hypoxic respiratory drive, diminish upper airway tone, blunt upper airway reflexes and decrease functional residual capacity. Ketamine is unique in that it does not produce significant depression of ventilation. Upper airway muscle tone is maintained, upper airway reflexes remain intact and FRC is not diminished.

Answer 29

Answer: B Rationale: Bupivicaine has a slower onset of action compared to the other agents because of its greater degree of ionization at physiologic pH.

Answer 30

Answer: A Rationale: The molecular structure of articaine contains an ester side chain which is rapidly inactivated by hydrolysis. The ester metabolite is not para-aminobenzoic acid; and thus not associated with allergic reactions as were the ester local anesthetics (e.g. procaine). The half life for articaine is 27 minutes, lidocaine 96 minutes, bupivicaine 162 minutes, and mepivicaine 114 minutes.

Answer 31

Answer: B Rationale: Propranolol, a nonselective beta-blocker will inhibit the effect of epinephrine binding to the 2 receptor resulting in a more pronounced effect of the epinephrine binding to the -receptor. This will result in an exaggerated hypertensive response and a reflex bradycardia. The suggestion is to administer 1 mL of local anesthetic with epinephrine 1:100,000 and evaluate the response in 5 minutes.

Answer 32

Answer: C Rationale: The inferior alveolar artery and vein are located posteriorly and laterally relative to the inferior alveolar nerve.

Answer 33

Answer: D Rationale: The concept of context-sensitive half-time describes the time necessary for the drug concentration to decrease a predetermined percentage after discontinuing a continuous intravenous infusion of a specific duration. Depending on the drug's lipid solubility and the efficiency of its clearance mechanism, the context-sensitive half-time increases in parallel with the duration of continuous intravenous administration. The time necessary for the plasma concentration of barbiturates like thiopental and methohexital is prolonged as drug sequestered in fat and skeletal muscles reenters the circulation to maintain plasma concentration. When multiple doses of fentanyl or alfentanil are administered or when there is continuous infusion of the drug, progressive saturation of inactive tissue sites occurs prolonging the duration of action and clearance of the drug from the plasma. Propofol is rapidly cleared from the plasma by tissue uptake and metabolism. The clearance of propofol is not significantly influenced by the duration of continuous intravenous infusion.

Answer 34

Answer: A Rationale: Etomidate is one of the few anesthetics that suppresses the adrenocortical axis. Etomidate causes adrenocortical suppression by producing a dose-dependent inhibition of the enzyme 11-beta-hydroxylase which is necessary for conversion of cholesterol to cortisol. This suppression lasts 4 to 8 hours after an induction dose of etomidate. Propofol, ketamine, methohexital do not suppress the adrenocortical axis.

Answer 35

Answer: A Rationale: Most of the barbiturates cause a decrease CNS activity and a suppression of seizure activity. Methohexital is an exception and has been shown to activate epileptic foci.

Answer 36

Answer: D Rationale: Propofol is the only agent in the group that has antiemetic effects. There is a low incidence of postoperative nausea and vomiting associated with propofol. The barbiturates do not have antiemetic properties and postoperative nausea and vomiting may be more common with etomidate and ketamine.

Answer 37

Answer: D Rationale: Administration of methohexital produces modest decreases in systemic blood pressure that are transient due to compensatory increase in heart rate. This decrease in systemic blood pressure is principally due to peripheral vasodilatation. The resulting dilation of peripheral capacitance vessels leads to pooling of blood, decreased venous return and the potential for decreases in cardiac output and systemic blood pressure.

Answer 38

Answer: D Rationale: Maximal brain uptake of methohexital occurs within 30 seconds after intravenous administration, accounting for the rapid induction of anesthesia. Prompt awakening after a single intravenous dose of methohexital reflects redistribution of these drugs from the brain to inactive tissue sites, especially skeletal muscles and fat. Large or repeated doses of methohexital may saturate inactive tissues sites, resulting in prolonged effects. When the inactive tissue sites are saturated, drug clearance becomes dependent on the rate of elimination.

Answer 39

Answer: C Rationale: Serotonin syndrome is characterized by confusion, agitation, tachycardia, fever, hyperreflexia, and myoclonus. Normeperidine is an active metabolite of meperidine metabolism and has a half-life of 15 to 30 hours in an adult. Normeperidine's elimination is dependent upon renal function and can accumulate with high repeated dosages or in the presence of renal impairment. Serotonin antagonists, SSRI and tricyclic antidepressants all may enhance the adverse/toxic effects of meperidine that results in serotonin syndrome.

Answer 40

Answer: A Rationale: Oxygenated hemoglobin absorbs less red light (600-750nm) and more infrared light (850-1000 nm) than deoxygenated hemoglobin. All pulse oximeters utilize 2 wavelengths of light, one in the red band and one in the infrared band. IN a healthy individual, maintenance of SpO2 of above 90% is evidence that the PaO2 is most likely higher than 60 mmHg. Dyshemoglobins include carboxyhemoglobin (COHb) and methmoglobin (MetHb) can affect the accuracy of pulse oximetry readings. COHb absorbs very little light in the infrared spectrum but much light in the visible red spectrum (hence the “cherry red” appearance of the patient with carbon monoxide poisoning), thus overestimating the O2 saturation as measured by pulse oximetry. Heavy smokers have COHb levels of 10-15% that may persist for up to 8 hours after the last cigarette.

Answer 41

Answer: C Rationale: Gastric emptying is influenced by volume (distention), osmolarity (protein and sugar), fat, and sold vs liquid (fat slows gastric emptying greater than carbohydrates or proteins). Cavell et al reported that the gastric emptying in healthy infants at 1 and 6 months of age was 48 minutes for human milk and 78 minutes for infant formula. There is insufficient evidence but the Task Force supports a fasting period of 6 hours or more before an elective procedure.

Answer 42

Answer: C Rationale: Meperidine is a phenylpiperidine opioid, but differs from other drugs in this category by its atropine-like characteristic with marked tachycardic effects and prominent histamine releasing propensity. This would account for the cutaneous erythema and vasodilative hypotension. Like other phenylpiperidines, it has a strong mu-receptor agonism which can cause significant respiratory depression. Remifentanil is largely devoid of histamine releasing effects which would mitigate against cutaneous erythema, but can cause peripheral vasodilation and hence drop blood pressure with a small amount of reflex increase in heart rate. Remifentanil, like other pure mu receptor agonists, can cause significant respiratory depression. Butorphanol is a mu receptor antagonist and pentazocine is a partial mu receptor antagonist while both are agonists of kappa receptors, hence their limited respiratory depression but significant analgesic properties. Neither of these agonist/antagonist medications exhibits significant histamine releasing propensities.

Answer 43

Answer: D Rationale: A one-compartment model involves administration of an intravenous medication intravascularly, and (relatively rapid) metabolism or elimination causing a more or less linear decrease in plasma drug concentration. A two-compartment model involves both more rapid initial elimination or metabolism of an intravascular drug plus the slower release of a drug into the blood from non-vascular tissues such as muscle or fat, causing a secondary beta phase of more slow decrease in plasma drug concentration by metabolism and/or elimination. The initial rapid pharmacologic onset of opioids is via their rapid initial crossing of the blood/brain barrier. With one bolus administration, many opioids are then rapidly redistributed to other tissues and the central nervous system effects are then ended. However, with continuous infusion or multiple bolus administration, depot storage of an opioid can occur and prolonged opioid effects can be manifest by a two-compartment release of drug over time. However, remifentanyl is so rapidly metabolized by ester hydrolysis that significant depot storage does not occur, and a one- compartment model of pharmacokinetics is approximated, causing rapid emergence from its effects after cessation of administration. Meperidine, morphine, and fentanyl undergo more slow hepatic degradation and follow a two-compartment model.

Answer 44

Answer: A Rationale: Levallorphan (a structural analog to the mu receptor agonist levorphanol) is an opioid antagonist; and its administration causes competitive binding at mu opioid sites throughout the nervous system. However, levallorphan exhibits mild kappa receptor agonism with analgesic properties. A patient with a heroin addiction may suffer acute withdrawl symptoms with administration of this or other opioid antagonist medications. Other opioid antagonists include naloxone and naltrexone. Tramadol is a synthetic analog of codeine and exhibits weak mu receptor agonism, and is useful for mild to moderate pain. Meperidine is a phenylpiperidine opioid agonist. Propoxyphene is a methadone analog with somewhat less mu agonist activity than codeine. Tramadol, meperidine, and propoxyphene will not precipitate opioid withdrawl.

Answer 45

Answer: C Rationale: Fentanyl can cause skeletal (including respiratory) muscle static contraction, especially when given as a bolus dose. This centrally mediated action can occur with bolus administration of any opioid, but is much more common with fentanyl and its cojoiners. If the patient cannot be adequately ventilated, opioid antagonist administration can be used to displace fentanyl from central nervous system binding sites thus this phenomenon, but this may not be advisable in the patient in whom a laryngeal mask airway has been inserted since gagging may result. Administration of a rapidly acting muscle relaxant can effect skeletal (hence respiratory) muscle paralysis and allow ventilation in this scenario. Addition of a volatile anesthetic agent, although causing some skeletal muscle relaxation, would not resolve the respiratory muscle tonic contracture quickly enough. Use of epinephrine for its beta-2 adrenergic effect would do nothing for this patient who is not suffering from bronchial muscle constriction. Insertion of a cuffed endotracheal tube might allow higher peak inspiratory pressure than is possible with a laryngeal mask airway, but would not treat the causative problem.

Answer 46

Answer: A Rationale: Alfentanil has a potency 1/10th that of fentanyl and is relatively rapidly metabolized by hepatic degradation. These two properties allow relative safety in intermittent bolus administration in a sedation technique, and have made this drug popular as an agent in an outpatient general anesthetic technique. Sufentanil has a shorter alpha half-life (by redistribution) and a shorter beta half life (by hepatic and renal metabolism) than does fentanyl. However, its potency is 10 times that of fentanyl and it is recommended for continuous intravenous infusion only, since a bolus administration of this extremely potent opioid can yield very high peaks of pharmacologic effect and side-effect. Remifentanil is equipotent to fentanyl. However, its rapid onset is associated with bradypnea, trunchal rigidity and bradycardia. Although it has been used as a bolus administration for procedures such as a retrobulbar block it is generally recommended for continuous infusion. Meperidine undergoes slower metabolization and repetitive administration can prolong recovery.

Answer 47

Answer: B Rationale: A dose of epinephrine greater than 2.1 mcg/kg can induce a dysrhythmia in a patient anesthetized with halothane. Correct dosing of epinephrine with the use of halothane is especially important in the pediatric population. The maximum safe epinephrine dose when halothane is used is generally considered to be 1.0 mcg/kg.

Answer 48

Answer: B Rationale: Carbon monoxide, produced as an end product of burning tobacco has 200x greater affinity than oxygen to the Hgb molecule. Carboxyhemoglobin which can be as high as 15%, predisposes a patient to perioperative hypoxia. Pulse oximetry fails to recognize the presence of carboxyhemoglobin as distinct from oxyhemoglobin. Therefore a patient with 10% COHb may display a saturation of 100% when in fact the actual saturation may be closer to 90%. In addition, carboxyhemoglobin has the effect of shifting the oxygen-dissociation curve to the left (less oxygen delivered to tissues). Ventilation, the mechanism of air exchange between the environment and the lungs, is not directly effected by carbon monoxide.

Answer 49

Answer: C Rationale: Midazolam, fentanyl, and propofol all cause a relaxation of the upper airway musculature, a depression of the hypoxic/hypercapneic respiratory drive and a depression of the pharyngeal and laryngeal reflexes. The patient's cough followed by stridorous sounds is suggestive of an irritation of the vocal cords resulting in a laryngospasm. Chest movement without air exchange which is implied may be secondary to upper airway obstruction, however, while this may not be completely relieved by a jaw thrust it would be anticipated that there would be some improvement.

Answer 50

Answer: Rationale: Pediatric patients have anatomic differences that make tracheal intubation more challenging. Their epiglottis is floppy and more difficult to manipulate. Their larynx lies at a more superior level; C3-C4 as opposed to the adult, where lies at C4-C5. This is an important anatomic consideration to have in mind for the correct placement of the ETT and position of the tip. The anterior attachment of the vocal cords is more caudal so they are not perpendicular to the airway as they are in the adults. These factors make it necessary to displace the tongue and mandible more in order to visualize the infant's vocal cords. Therefore, straight laryngoscopes blades are used more commonly to intubate the trachea of children.

Answer 51

Answer: B Rationale: A right to left intracardiac shunt will result in less blood perfusing the lungs. This will result in an increase in alveolar partial pressure but also a decrease in arterial partial pressure. A right to left intracardiac shunt could potentially speed up an intravenous induction because venous blood carrying the IV induction agent will return to the heart and bypass the pulmonary circulation, reaching the brain more quickly. A patient with Tetralogy of Fallot is a classic example of a patient with a right to left intracardiac shunt. Functional residual capacity is the volume of lung after the end of a normal TV expiration. A smaller volume will reach a higher anesthetic concentration more quickly than a larger volume. A small functional residual capacity will allow the alveolar concentration to quickly approach the inspired concentration, speeding up induction. Pediatric patients have a small FRC and high alveolar ventilation resulting in more rapid inhalation induction compared to adults. Increasing alveolar ventilation will replace more anesthetic taken up by the pulmonary bloodstream, maintaining a higher alveolar concentration and thus speeding induction. An agent with low blood gas solubility will equilibrate rapidly resulting in a more rapid induction.

Answer 52

Answer: C Rationale: While undergoing a general anesthetic, children without lung disease may lose as much as 45 percent of their FRC. Owing to a higher oxygen consumption and greater loss of FRC in children during general anesthesia, hypoxia develops in a matter of seconds. To compensate for the higher oxygen consumption, children have a higher blood volume per kg or compared to adult-(80-100 cc/kg children and 65-70cc/kg for adults). Children should have their ventilation controlled during anesthesia because hypoventilation exacerbates their tendency toward hypoxia. Atelectasis may occur in mechanically ventilated children, but is more likely to occur in children who breathe spontaneously. Children with pulmonary diseases may lose even more of the FRC, exposing them to increasing ventilation-perfusion mismatch and hypoxia. An increased inspired oxygen concentration and application of positive end-expiratory pressure (PEEP) may partially restore FRC. However, PEEP must be applied carefully.

Answer 53

Answer: B Rationale: Neonates, infants, and children have an increased body surface area relative to weight. Because they cannot shiver to create or maintain body heat they rely on a less efficient process called non-shivering thermogenesis. This process is dependent upon the fact that children have a greater amount of brown fat (so named because of its rich vascular supply) than adults. When the newborn is cold stressed, oxygen consumption will increase and result in the release of norepinephrine (NE). NE will react with the Lipases in the brown fat to breakdown fat into triglycerides. The cascade continues to as triglycerides are metabolized to glycerol and non-esterified fatty acids (NEFA). These NEFA are further degraded under the needed heat generating process to form carbon dioxide and water.

Answer 54

Answer: C Rationale: Morbid obesity is defined as a body weight in excess of 100 lbs over ideal weight or a body mass index of 40 or greater. There are a variety of adverse changes associated with obesity. Pulmonary function changes in obese patients suggest restrictive pulmonary disease characteristics. PaO2 is decreased by obesity as a result of ventilation/perfusion mismatches. Despite this, PaCO2 and the ventilatory response to PaCO2 remains normal. Functional residual capacity is decreased and is accentuated by supine positioning and under anesthesia.

Answer 55

Answer: C Rationale: Large doses of prilocaine, generally greater then 600 mg, can result in methemoglobinemia in selected patients. Intravenous doses of articaine have been reported to cause similar problems. This occurs as a result of one of the metabolites of the drug converting reduced hemoglobin to methemoglobin. The patient will experience cyanosis with dark blood. Pulse oximetry remains normal since the monitor mistakenly interprets methemolgobin as oxyhemoglobin but the actual oxygen carrying capacity is decreased resulting in the cyanosis. Small doses of methylene blue ( 1-2 mg/kg) will convert the methemoglobin back to reduced hemoglobin

Answer 56

Answer: D Rationale: An increase in heart rate is usually the earliest and most consistent sign to be detected. An increase in end-tidal CO2 is usually the most sensitive sign in detecting malignant hyperthermia. While increase temperature and muscle rigidity are hallmark signs of malignant hyperthermia, these manifestations are less sensitive and may not present as early as the tachycardia and elevated end-tidal CO2. Masseter muscle rigidity should be distinguished from skeletal muscle rigidity and occurs early.

Answer 57

Answer A Rationale: Patients who have acute intermittent porphyria do not tolerate barbiturates. The use of these drugs could precipitate an attack, which would present with abdominal pain, tachycardia and hypertension, seizures and autonomic nervous system disorders. Propofol is safe to use. Midazolam and ketamine are probably safe to use.

Answer 58

Answer A Rationale: Vagal maneuvers, such as the Valsava maneuver can be tried first. Vagal maneuvers are most effective if attempted immediately after onset. Adenosine is the first drug of choice if vagal maneuvers are ineffective.

Answer 59

Answer: D Rationale: Magnesium should be considered the first drug of choice in the treatment of torsades de pointes. It is administered as magnesium sulfate 1 to 2 grams over 1 to 2 minutes. Traditional anti-arrhythmic therapy is not likely to be successful.

Answer 60

Answer: B Rationale: Cessation of smoking should allow for gradual improvement in lung function. Nicotine with a half-life of approximately 30-60 minutes would fall precipitously with cessation of smoking for four hours prior to administration of the anesthesia. Although of some benefit, the stimulation of the sympathoadrenal system would take longer to normalize. Carboxyhemoglobin levels should approach that of a non-smoker after a smoke free period of approximately 48 hours. This should allow for increased availability of hemoglobin for oxygen transport. The hypersecretion of mucous requires a period of approximately six weeks to decline to normal levels after cessation of smoking. Alveolar macrophage, antimicrobial function has been shown to take six months or more to improve to that of a non-smoker. Narrowing of the bronchial airways and air trapping is another problem seen with smoking. Improvement in pulmonary function test generally requires a minimum period of six weeks of abstinence.

Answer 61

Answer: D Rationale: Sympathetic maintained pain (SMP) results from tonic activity in myelinated mechanoreceptor afferents, whose activity is induced by sympathetic efferent actions on sensory receptors, and this afferent input causes tonic firing in previously sensitized wide-dynamic (WDR) or mulitreceptive neurons that are part of a central nociceptive pathway. A burning painful sensation results from this chain of actions. Insert Reference: Gregg JM: Studies of traumatic neuralgia in the maxillofacial region: symptom complexes and response to microsurgery. J Oral Maxillofac Surg 48:135, 1990 Roberts W: A hypothesis on the physiological basis for causalgia and related pain. Pain 24:297, 1986 Raja SN. Turnquist JL. Meleka S. Campbell JN. Monitoring adequacy of alpha- adrenoceptor blockade following systemic phentolamine administration. [Clinical Trial. Controlled Clinical Trial. Journal Article] Pain. 1996;64):197-204, 1996

Answer 62

Answer: D Rationale: Cluster headache has a 6:1 male predilection, is most commonly periorbital and excruciating, and is strictly unilateral. Episodes last from 15 – 180 minutes, but most commonly from 30 – 60 minutes. Occurrence is from one every other day to eight per day, and they tend to “cluster” over time; each cluster lasts from 1 – 2 months, with one or two clusters per year. Pain is commonly described as burning, piercing, or neuralgic, and ipsilateral autonomic symptoms such as lacrimation, rhinorrhea, miosis, and/or ptosis occur. Migraine typically exhibits throbbing unilateral pain lasting from 4 – 72 hours, nausea, photophobia, and exacerbation by physical activity. Trigeminal neuralgia can be differentiated from cluster headache because pain is transient and not associated with autonomic signs/symptoms. Tension headache is commonly bandlike and bilateral, lasts 30 minutes to seven days, of mild to moderate intensity that does not prohibit activity, and not associated with nausea/vomiting or photophobia. Reference: Smetana, GW. The diagnostic value of historical features in primary headache syndromes: a comprehensive review. Arch Int Med 200;160:2729-37.

Answer 63

Answer: B Rationale: The four categories of primary headache include migraine, tension-type, cluster headache, and other trigeminal autonomic cephalgias and other primary headaches. This man's history is most compatible with cluster headache. Cluster headache is a distinct clinical syndrome affecting men more than woman, with attacks accompanied by ipsilateral lacrimation, nasal discharge, ptosis, conjunctival injection, and pupillary change. The features most predictive of migraine are nausea, photophobia, phonophobia, exacerbation with physical activity. Meningismus is associated such acute events as subarachnoid hemorrhage. Reference: Saper JR. Headache disorders. Med Clin North Am 1999; 83:663-90 Smetana, GW. The diagnostic value of historical features in primary headache syndromes. A comprehensive review. Arch Intern Med 2000; 160:2729. Bahra, A, May, A, Goadsby, PJ. Cluster headache: A prospective clinical study with diagnostic implications. Neurology 2002; 58:354. Lipton, RB, Bigal, ME, Steiner, TJ, et al. Classification of primary headaches. Neurology 2004; 63:427.

Answer 64

Answer: C Rationale: Glossopharyngeal neuralgia is defined as paroxysmal pain in areas innervated by cranial nerves IX and X. Pain may be experienced in the ear, larynx, tonsillar region, and tongue. It is almost always unilateral. Triggers include chewing, swallowing, coughing, speaking, and yawning. Severe attacks have been associated with bradycardia/syncope through the vagal motor nucleus. Carotodynia is pain that originates in the carotid artery. The pain is usually unilateral, provoked by swallowing, coughing, or neck movement, and typically lasts for several days to months. Eagle's syndrome is loosely associated with ossification of the stylohyoid ligament. Dull pharyngeal and neck pain possibly provoked with swallowing and head turning is described. Palpation of the tonsillar fossa and/or hyoid may illicit pain. Sphenopalatine (greater superficial petrosal) neuralgia presents as unilateral, episodic pain in the perinasal region, associated with nasal congestion. Some case may be attributable to cluster headache and may not represent a unique diagnostic entity. Reference: Rushton, JG, Stevens, JC, Miller, RH. Glossopharyngeal (vagoglossopharyngeal) neuralgia: a study of 217 cases. Arch Neurol 1981; 38:201 Elias, J, Kuniyoshi, R, Valadao, W, et al. Glossopharyngeal neuralgia associated with cardiac syncope. Arq Bras Cardiol 2002; 78:515 Fini, G, Gasparini, G, Filippini, F, et al. The long styloid process syndrome or Eagle's syndrome. J Craniomaxillofac Surg 2000; 28:123

Answer 65

bind to chloride gated GABA receptor, increasing frequency of inward chloride flow, hyper polarizing cell membranes and reducing neuronal transmission

Answer 66

sedation, anxiolysis, anterograde amnesia, muscle-relaxing properties and anticonvulsant activity.

Answer 67

flumazenil

Answer 68

IV - moderate sedation - lipid soluble and carried in organic solvent - painful when injected 2. 5-5 mg increments every few minutes - longer elimination time and numerous active metabolites compared to midazolam, may contribute to lingering sedative effects

Answer 69

5-10 mg for preoperative anxiolysis and minimal sedation

Answer 70

highly lipid soluble with slow reentry into central circulation, leading to elimination half life of 24 to 96 hours. Is metabolized into two active metabolites, desmethyldiazepam and oxazepam Active metabolites and parent drug are partially eliminated in bile and can result in resedation several hours later, especially after ingestion of fat-rich meal

Answer 71

water soluble at pH

Answer 72

conscious sedation 0.05 to 0.15 mg/kg in divided doses, titrated to effect, typically given in 1-2 mg boluses every few minutes. Peak effect in 5 minutes -decrease dose when given with opioids or other sedatives

Answer 73

0.5mg/kg orally (max 15 mg) for preoperative sedation or up to 1mg/kg orally (max 15 mg) for procedural sedation. clinical effect from PO administration will be seen 15-20 minutes.

Answer 74

a sleep adjunct, can be used off label for anxiolysis and moderate sedation at a dose of 0.25 to 0.5 mg for an adult. effects observed in 30 to 45 minutes, peaking a little over an hour with clinically effective sedation lasting from 60 to 90 minutes

Answer 75

highly specific competitive antagonist for the benzodiazepine receptor. - will reverse benzo sedation, excessive disinhibition and the additive ventilatory depression related to benzos when used with opioids. - administered electively at 0.2mg IV followed by 0.1mg at one minute intervals to a total of 1mg - Emergency situations 0.5 to 1 mg or more - flumazenil lasts 30 to 60 minutes and may require redosing because agonist drug activity may outlast the reversal effects.