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A 32-year-old obese female presents to the emergency with fever, right upper quadrant pain, and vomiting for the past 8 hours. She is diagnosed with acute cholecystitis and is taken emergently to the operating room for a laparoscopic cholecystectomy. During the procedure, she is kept anesthetized with sevoflurane and paralyzed with vecuronium. At the end up the procedure, neuromuscular blockade is reversed with intravenous neostigmine, at which time the patient™s heart rate drops from 60 beats/min to 15 beats/min. The patient subsequently becomes asystolic, and a code is called. The patient is successfully resuscitated with intravenous epinephrine and chest compressions. This complication could have been prevented by co-administering neostigmine with which of the following?
A. Glycopyrrolate
B. Bethanechol
C. Ephedrine
D. Edrophonium
E. Potassium
F. Pilocarpine
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Choice (A) is the correct answer. Neostigmine is an acetylcholinesterase inhibitor that is used to reverse neuromuscular blockade by increasing acetylcholine levels at the neuromuscular junction. Acetylcholine also acts on cardiac muscarinic receptors and results in a decrease in heart rate by decreasing conduction through the atrioventricular node as well as decreasing the sinoatrial node rate. Acetylcholine also causes peripheral arterial vasodilation, which when combined with bradycardia can potentially result in cardiac arrest. Other effects of increased acetylcholine levels include increased GI motility, lacrimation, salivation, pupillary constriction, and bronchial constriction. To counteract the muscarinic effects of acetylcholine, anti-muscarinic drugs such as glycopyrrolate or atropine are administered simultaneously with neostigmine to prevent bradycardia, hypotension, and potential cardiovascular collapse. Bethanechol (Choice B) is direct cholinergic agonist. Ephedrine (Choice C) is a vasoactive drug that stimulates norepinephrine release from nerve endings. It also has direct alpha and beta activity. Edrophonium (Choice D) is an acetylcholinesterase inhibitor similar to neostigmine but with a more rapid onset and a shorter duration of action. Potassium (Choice E) is incorrect. Pilocarpine (Choice F) is a direct-acting cholinergic agonist.
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thanku for good q's and explanations...
