e201CHAPTER 136 Board Review Questions Rationale While all of these answers can result in altered or depressed men tal status, only the prolonged effect of succinylcholine would re sult in the train o[.]
CHAPTER 136 Board Review Questions Rationale While all of these answers can result in altered or depressed mental status, only the prolonged effect of succinylcholine would result in the train of four findings Pseudocholinesterase deficiency encompasses a number of genetic variants resulting in varying duration of paralysis dependent on the amount of butyrylcholinesterase available to resolve the effect of the depolarizing muscle relaxant The mainstay of therapy is mechanical ventilation and supportive care until return of motor function and adequate respiratory effort Which of the following is associated with propofol infusion syndrome? A Hypokalemia B Metabolic alkalosis C Rhabdomyolysis D Tachycardia Preferred response: C Rationale Propofol infusion syndrome (PRIS) is characterized by severe intractable bradycardia that leads to cardiac failure, severe metabolic acidosis, hyperlipidemia, rhabdomyolysis with consequent hyperkalemia, and renal failure Prolonged propofol infusions (more than 48 hours) and infusion rates greater than mg/kg/h have been linked to PRIS Priming factors such as critical illness (respiratory failure and traumatic brain injury) and triggering factors such as catecholamine and steroid infusion are associated with the syndrome The underlying mechanism appears to be an inhibition of mitochondrial electron transport and impairment in oxygen utilization As a result, there is a decreased ATP production and a decreased mitochondrial lipid metabolism, with an accumulation of toxic long fatty acid chains that are arrhythmogenic Pediatric patients appear more susceptible than adults secondary to low glycogen stores and high need for fat metabolism Which of the following statements regarding local anesthetic agents is correct? A Amino amide local anesthetics are metabolized by plasma and tissue esterases B Compared with adults, the unbound fraction of local anesthetics is lower in children C Compared with adults, infants are at a lower risk for local anesthetic toxicity D Compared with adults, the duration of action of local anesthetic agents is shorter in infants Preferred response: D Rationale Local anesthetic agents are classified as amino esters (cocaine, tetracaine, chloroprocaine, and prilocaine) or amino amides The amino amides include bupivacaine, ropivacaine, levobupivacaine, and lidocaine and are potent sodium channel blockers At toxic blood concentrations they can cause seizures, cardiac arrhythmias, and cardiac arrest that can be resistant to resuscitation Children are more at risk from local anesthetic toxicity because of their lower serum concentrations of a1-acid glycoprotein (AAG) and albumin, which are the binding proteins for local e201 anesthetics (LA) Therefore the unbound fraction of LA, which is the active drug, is increased, making infants and children more susceptible to local anesthetic toxicity (LAST) Another factor that can influence LAST in neonates and children is the slower metabolism and elimination of the local anesthetic agents The potency and duration of local anesthetic agents depend on lipophilicity, degree of ionization, protein binding, and the vasoconstricting properties of the drug In general, the duration of action of local anesthetic agents is shortest in neonates and infants Metabolism of amides is by the liver’s P-450 enzyme system, while metabolism of the ester compounds is by plasma esterases (butyrylcholinesterase) and tissue esterases When compared with pediatric liver transplant patients who not have an increased risk for perioperative bleeding, pediatric liver transplant patients who receive recombinant activated factor VII (rFVIIa) have been shown to have which of the following? A An increase in operating time B An increased number of thromboembolic events C No difference in blood loss D The same number of thromboembolic events Preferred response: C Rationale rFVIIa is an analogue of the naturally occurring activated FVII and is a powerful hemostatic agent It is approved by the US Food and Drug Administration for use in persons with congenital or acquired hemophilia with inhibitors who are actively bleeding or for prophylaxis before invasive surgery or procedures rFVIIa directly enhances thrombin generation locally at the site of endothelial damage, where tissue factor is exposed, and indirectly enhances it on the activated platelet surface, creating the thrombin burst that generates enormous amounts of fibrin mesh in proximity to the damaged vasculature Since it began to be marketed in 1999 in the United States, the number of publications regarding the off-label use for life-threatening hemorrhages of various origins in nonhemophiliac patients has exponentially increased, giving rFVIIa a potential role as a universal hemostatic agent Pediatric liver transplants have a higher incidence of vascular graft thrombosis because of the smaller caliber of the vascular grafts, and it is feared that the administration of rFVIIa can increase the incidence of vascular graft thrombosis Kalicinski et al reviewed 89 consecutive patients from to 20 years of age who underwent cadaveric liver transplant Twenty-eight of these patients had a high risk of intraoperative blood loss and received rFVIIa before undergoing the transplant procedure When they were compared with 61 patients who had no increased intraoperative risk of blood loss, no difference was noted in blood loss, operating time, reexploration, and hospital stay Interestingly, no thromboembolic events were observed in the group that received rFVIIa, whereas in the 61 patients who did not receive rFVIIa, had hepatic artery thrombosis, had portal vein thrombosis, and had hepatic vein thrombosis The authors suggest that despite the use of rFVIIa, the overall hemostatic balance remains modestly hypocoagulable e202 S E C T I O N XV Pediatric Critical Care: Board Review Questions Chapter 129: Anesthesia Principles and Operating Room Anesthesia Regimens Which of the following suggests that endotracheal intubation or airway management may be problematic? A Body mass index in 95th percentile B Full extension and flexion of the neck C Mallampati class IV D Mouth opening of fingerbreadths E Thyromental distance of fingerbreadths Preferred response: C Rationale The Mallampati grading system describes the visualization of the oropharynx including the uvula and tonsillar pillars A Mallampati grade of IV where the uvula and the tonsillar pillars cannot be visualized correlates with the potential for problematic airway management Which agent is most effective in resuscitation from local anesthetic systemic toxicity (LAST)? A Amiodarone B Epinephrine C Intralipid D Propofol E Vasopressin Preferred response: C Rationale Current guidelines from the American Society of Anesthesiologists (ASA) and the American Society of Regional Anesthesia and Pain Medicine (ASRA) recommend the ready availability and immediate administration of intralipid for LAST The intralipid is administered as a bolus dose followed by an infusion and frequently results in return of spontaneous circulation (ROSC) Which agent may depress adrenal function? A Etomidate B Thiopental C Methohexital D Ketamine E Propofol Preferred response: A Rationale Etomidate inhibits 11b-hydroxylase, a key enzyme in the adrenal cortex’s production of corticosteroids Although there is no direct evidence-based medicine to demonstrate an effect on outcome in the pediatric population, caution is suggested when using this agent in patients with systemic sepsis Which of the volatile anesthetic agents is no longer in clinical use due to its association with perioperative cardiac arrest in children? A Desflurane B Enflurane C Halothane D Isoflurane E Sevoflurane Preferred response: C Rationale Halothane has significant negative inotropic and chronotropic properties and was the primary medication implicated in perioperative cardiac arrest in infants and children With the introduction of the newer agent, sevoflurane, which provided an effective alternative for inhalational induction, the use of halothane decreased and then stopped Which of the following opioids has the shortest half-life? A Alfentanil B Fentanyl C Meperidine D Morphine E Remifentanil Preferred response: E Rationale Remifentanil is metabolized by plasma esterases and has an effective plasma half-life of 8–10 minutes in patients of all ages, including neonates Which of the following anesthetic agents or metabolite may impair vitamin B12 metabolism? A Halothane B Ketamine C Nitrous oxide D Propofol Preferred response: C Rationale When used for procedural sedation on repeated occasions, nitrous oxide impairs vitamin B12 metabolism through inactivation of methionine synthetase This may lead to bone marrow impairment with megaloblastic anemia and deterioration of the posterior columns of the spinal cord and neurologic impairment These effects may occur not only in patients but also in healthcare workers with chronic exposure, thereby mandating effective scavenging of exhaled gases to avoid environmental pollution whenever nitrous oxide is administered Which of the following agents may increase intracranial pressure (ICP)? A Morphine B Propofol C Sevoflurane D Thiopental Preferred response: C Rationale Barbiturates (e.g., thiopental and thiamylal) and propofol decrease the cerebral metabolic rate for oxygen, resulting in reflex cerebral vasoconstriction and a decrease in cerebral blood volume, thus decreasing the ICP Morphine has no effect on cerebral dynamics All of the inhalational anesthetic agents, including sevoflurane, result in nonspecific cerebral vasodilation, which increases ICP in patients with altered intracranial compliance The effect of the inhalational anesthetic agents can be partially blunted with hyperventilation CHAPTER 136 Board Review Questions e203 Malignant hyperthermia (MH) may be triggered by which of the following agents? A Etomidate B Ketamine C Propofol D Succinylcholine Preferred response: D Rationale The hypermetabolic state of MH leads to increased CO2 production as well as oxygen desaturation and lactic acidemia The result is mixed metabolic and respiratory acidosis In addition, muscle breakdown releases intracellular potassium The resulting hyperkalemia must be aggressively treated before malignant arrhythmias develop Rationale MH is an inherited disorder of muscle metabolism affecting the calcium channel, whereby there is ongoing activation of the channel with increases in intracellular calcium concentrations and increased muscle metabolism This phenomenon results in hypercarbia, hyperthermia, acidosis, and rhabdomyolysis with hyperkalemia MH can be triggered by succinylcholine or any of the inhalational anesthetic agents Treatment is removal of the offending agent, symptomatic therapy directed against metabolic derangements, and dantrolene to block ongoing calcium release 2 A previously healthy 7-year-old male has been successfully treated intraoperatively with dantrolene, in the setting of a presumed malignant hyperthermia (MH) reaction that occurred during strabismus surgery Hyperthermia and muscular rigidity have resolved, blood gas analysis is now within normal limits, and the intubated patient is transferred to the pediatric intensive care unit (PICU) for further care Should further dantrolene be administered during the patient’s initial 24 hours in the PICU? A No, not unless muscular rigidity reoccurs B No, not unless blood gas analysis reveals recurrence of respiratory acidosis C Yes, 2.5 mg/kg dantrolene should be given every 4–6 hours to prevent recrudescence D Yes, mg/kg dantrolene should be given every 4–6 hours to prevent recrudescence Preferred response: D Which of the following is the least potent anesthetic, that is, has the highest minimum alveolar concentration (MAC)? A Desflurane B Halothane C Isoflurane D Nitrous oxide Preferred response: D Rationale MAC is a judge of the potency of an inhalational anesthetic agent It describes the expired concentration of the agent required to prevent movement in 50% of patients in response to a surgical stimulus (i.e., incision) Nitrous oxide has a MAC of greater than 100% and is therefore the least potent of the inhalational anesthetic agents 10 Negative chronotropic effects are most likely with which agent? A Desflurane B Isoflurane C Nitrous oxide D Sevoflurane Preferred response: D Rationale All of the inhalational anesthetic agents can have adverse hemodynamic effects These are generally minimal with nitrous oxide and vary depending on the potent inhalational anesthetic agent used Desflurane and isoflurane generally result in vasodilation, which results in reflex tachycardia Sevoflurane has some direct negative chronotropic effects and therefore may result in a slowing of the heart rate Chapter 130: Malignant Hyperthermia Laboratory analysis during a fulminant malignant hyperthermia (MH) episode is most likely to reveal which of the following? A Metabolic alkalosis, hyperkalemia B Mixed metabolic and respiratory acidosis; hyperkalemia C Respiratory acidosis with metabolic compensation; hyperkalemia D Respiratory acidosis with metabolic compensation; hypokalemia Preferred response: B Rationale Given that recrudescence of MH is seen in approximately 20% of cases and can progress to fulminant MH, the Malignant Hyperthermia Association of the United States (MHAUS) recommends continued dantrolene therapy for at least 24 hours following initial treatment and stabilization Dantrolene should be continued as mg/kg intravenously every 4–6 hours Continuous infusion at 0.25 mg/kg/h is an alternative, but is not superior to intermittent bolus, and may increase the risks associated with extravasation of dantrolene Which of the following are the most common complications of dantrolene therapy? A Bradycardia; urinary retention B Bronchospasm; hyperkalemia C Muscle weakness; phlebitis D Ventricular arrhythmias; diplopia Preferred response: C Rationale In a review of MH cases submitted to the North American Malignant Hyperthermia Registry (NAMHR) between 2007 and 2013, the most common complications associated with dantrolene therapy were muscle weakness (20.4%), phlebitis (9.9%), hyperkalemia (6.6%), respiratory failure (2.6%), and GI upset (2.0%) e204 S E C T I O N XV Pediatric Critical Care: Board Review Questions Volatile inhaled anesthetics are being considered in the management of a pediatric patient with severe, refractory asthma in the ICU The patient’s mother states that she has a history of malignant hyperthermia (MH) under anesthesia She and her son underwent genetic testing, and he does not share her RYR1 genetic mutation Which of the following is true regarding the safety of administering volatile inhaled anesthetics to this pediatric patient? A Genetic testing does not affect the probability of this patient’s MH susceptibility B Given the genetic testing results, volatile anesthetics are definitively safe in this patient C Volatile anesthetics can be safely used in this setting, because only general anesthetic doses of volatile inhaled anesthetics trigger MH D While MH susceptibility can only be ruled out by muscle contracture testing, the lack of the familial RYR1 mutation decreases the probability of MH susceptibility Preferred response: D Rationale While only muscle contracture testing can definitively rule out MH susceptibility, this invasive test is only performed at specialized centers and is not practical in this acute setting And while the lack of the familial RYR1 mutation does not definitively rule out MH susceptibility, this information is reassuring It may be reasonable to consider volatile anesthetics in this patient, with close attention to any signs of malignant hyperthermia, and with dantrolene readily available The earliest sign of malignant hyperthermia (MH) is which of the following? A Hypoxia B Hyperthermia C Hypercarbia D Masseter spasm Preferred response: C Rationale The initial signs of an episode of MH are nonspecific Hypercarbia is the earliest sign of MH Tachycardia and dysrhythmias may also occur early in the course of an episode of MH Mottled cyanosis of the skin and generalized muscle rigidity may be present Masseter spasm has been claimed to be an early sign of MH Later, temperature elevation occurs The pathophysiologic mechanism responsible for the manifestations of malignant hyperthermia (MH) is which of the following? A Excessive serotoninergic activity at 5-HT1A receptors B Excessive stimulation of a-adrenergic receptor C Increase in sarcoplasmic sodium concentration D Increase in sarcoplasmic calcium concentration Preferred response: D Rationale MH is a clinically heterogeneous disorder in which a marked increase in the metabolic rate of genetically abnormal muscle can result in destruction of the muscle and multiorgan system failure The underlying biochemical defect is a sudden increase in the concentration of calcium ion in the sarcoplasm An increased metabolic rate of muscle produces a load of acid sufficient to overwhelm the buffering capacity of the body and the ability of the lungs to excrete carbon dioxide Increased oxygen demand and the concomitant sympathetic response challenge the cardiovascular system Neuroleptic malignant syndrome (NMS) resembles MH in clinical findings, with the exception that the time course of NMS is over hours to days rather than minutes to hours NMS occurs only in association with a pharmacologic trigger or potent neuroleptic agents NMS is related to the blockade of dopamine receptors The dopamine antagonist bromocriptine has been used successfully to treat this disorder The serotonin syndrome is caused by excessive serotoninergic activity at the 5-HT1A receptors in the central nervous syndrome The symptoms of serotonin syndrome include rapid onset of cognitive and behavioral changes, autonomic dysfunction, and neuromuscular abnormalities Fever can be extreme Which of the following tests is most likely to be helpful in evaluating for the presence of malignant hyperthermia (MH)? A Arterial lactate B Elevation of creatine phosphokinase C Elevation of myoglobin D Venous blood gas Preferred response: D Rationale The test that is most likely to be helpful in assessing the presence of MH is venous blood gas analysis Elevated carbon dioxide (CO2) tension is apparent in mixed venous blood before it is abnormal in arterial blood during an episode of MH An increase in lactate release from muscle occurs before a decrease in the partial pressure of oxygen in venous blood is observed during an episode of MH If venous blood indicates significant acidosis, partial pressure of CO2 greater than 60 torr, and bicarbonate less than 19 mEq/L and the history of the patient is consistent with MH, the physician may assume that the patient is experiencing an episode of MH and treat the patient accordingly Which of the following drugs can cause hyperkalemia and myocardial depression when given to a patient with malignant hyperthermia (MH) who is being treated with dantrolene? A Calcium channel blockers B Procainamide C Lidocaine D Procainamide Preferred response: A Rationale Cardiac dysrhythmias may occur with MH but usually stop when the episode is adequately treated with dantrolene Lidocaine may be administered with the usual precautions Before lidocaine was accepted as a drug that was unlikely to trigger MH, procainamide was the antidysrhythmic of choice during an episode of MH Procainamide is no longer recommended for treatment of MHsusceptible patients Calcium channel blockers are not indicated for patients with MH because they may cause severe hyperkalemia and cardiovascular collapse in the presence of MH CHAPTER 136 Board Review Questions e205 Chapter 131: Neuromuscular Blocking Agents Hyperkalemia is a lethal adverse effect associate with which neuromuscular blocking agent: A Cis-atracurium B Pancuronium C Rocuronium D Succinylcholine E Vecuronium Preferred response: D Rationale Succinylcholine is the only depolarizing neuromuscular blocking agent As such, it binds to and activates the nicotinic acetylcholine receptor on the muscle membrane This process opens potassium channels with the release of intracellular potassium With various myopathic or neurologic conditions, there may be a proliferation of receptors away from the normal site (extra-junctional receptors) that will result in an excessive release of potassium from the intracellular site when they are activated Which of the following neuromuscular blocking agents is not dependent on hepatic or renal elimination? A Cis-atracurium B Pancuronium C Rapacuronium D Rocuronium E Vecuronium Preferred response: A Rationale Cis-atracurium undergoes Hoffman degradation, a nonenzymatic, temperature and pH dependent process that does not require renal or hepatic metabolism Which of the following neuromuscular blocking agents was demonstrated to cause significant changes in airway resistance and compliance? A Cis-atracurium B Pancuronium C Rapacuronium D Rocuronium E Vecuronium Preferred response: C Rationale Following its introduction for clinical use, there were reports of profound and even potentially fatal bronchospasm associated with the administration of rapacuronium Although these problems were initially postulated to result from an inadequate depth of sedation/anesthesia during airway instrumentation, subsequent studies suggested a direct effect on the cholinergic pathways of the airway Subsequent work further defined the potential mechanisms including alterations in cholinergic function with antagonism of the M2 muscarinic receptor, augmentation of acetylcholine effects at the M3 muscarinic receptor, and potentiation of vagal nerve and acetylcholine-induced bronchoconstriction 4 Which of the following increases resistance to the effects of nondepolarizing neuromuscular blocking agents? A Anticonvulsant agents B Hypermagnesemia C Hypokalemia D Hypothermia E Volatile anesthetic agents Preferred response: A Rationale Resistance to the effects of nondepolarizing neuromuscular blocking agents develops with the chronic administration of anticonvulsants This effect relates not only to increased hepatic metabolism but also a mild upregulation of acetylcholine receptors That latter effect is a direct effect on the neuromuscular junction related to a mild neuromuscular blocking effect of phenytoin Which of the following neuromuscular blocking agents undergoes hepatic metabolism with the production of metabolites that have significant clinical effects, especially in patients with renal insufficiency or failure? A Atracurium B Mivacurium C Rocuronium D Succinylcholine E Vecuronium Preferred response: E Rationale Although both vecuronium and rocuronium undergo hepatic metabolism, only vecuronium produces significant quantities of water-soluble, renally eliminated metabolites with neuromuscular blocking effects The metabolism of which of the following neuromuscular blocking agents results in a potentially epileptogenic metabolite? A Cis-atracurium B Pancuronium C Rocuronium D Vecuronium Preferred response: A Rationale Cis-atracurium undergoes Hoffman degradation, a nonenzymatic process, which results in the breakdown of cis-atracurium During this process, laudanosine is released Although its clinical effects are relatively unknown in man, animal studies suggest that it may lower the seizure threshold Which neuromuscular blocking agent (NMBA) can be reversed with sugamadex? A Atracurium B Cis-atracurium C Rocuronium D Succinylcholine Preferred response: C ... intracranial pressure (ICP)? A Morphine B Propofol C Sevoflurane D Thiopental Preferred response: C Rationale Barbiturates (e.g., thiopental and thiamylal) and propofol decrease the cerebral metabolic rate... repeated occasions, nitrous oxide impairs vitamin B12 metabolism through inactivation of methionine synthetase This may lead to bone marrow impairment with megaloblastic anemia and deterioration of... the safety of administering volatile inhaled anesthetics to this pediatric patient? A Genetic testing does not affect the probability of this patient’s MH susceptibility B Given the genetic testing