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Review Question - QID 217276

QID 217276 (Type "217276" in App Search)
A 54-year-old woman presents to her primary care physician with a 3-month history of fatigue. She says that she typically begins the day feeling rested but quickly becomes exhausted after any type of sustained activity. In particular, she notices that when she goes grocery shopping, she will drop the bags after a short period of time. She also sees double after trying to watch a movie for a while. On physical exam, she is found to have progressive bilateral eyelid drooping when asked to look upwards. She is worried because she is planning to have a total hip replacement for severe hip pain and is worried that these symptoms might affect her ability to recover after surgery. With which of the following anesthetic agents would this patient have the most pronounced sensitivity to medication effects?

Bupivacaine

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Ketamine

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Propofol

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Succinylcholine

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Vecuronium

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0/0

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This patient who presents with weakness with prolonged activity as well as ptosis when looking upwards most likely has myasthenia gravis. Patients with myasthenia gravis are particularly sensitive to the effects of non-depolarizing neuromuscular blockade agents such as vecuronium.

Myasthenia gravis is an autoimmune disease in which autoantibodies are produced against proteins of the neuromuscular junction, most commonly the nicotinic acetylcholine receptor (AChR). Patients will therefore present with fluctuating weakness that is worse after prolonged activity or at the end of the day. Patients will classically also have symptoms of ocular fatigue such as diplopia and ptosis. Of note, since these patients have an autoimmune blockade of the acetylcholine receptor, they are particularly sensitive to anesthetic agents that also function as competitive inhibitors of AChR such as vecuronium. Patients with prolonged blockade who were administered non-depolarizing paralytic agents such as vecuronium can also be treated with sugammadex if reversal is needed emergently.

Schaller and Fink discuss how prolonged neuromuscular blockade by non-depolarizing acetylcholine receptor inhibitors such as vecuronium can be treated by the reversal agent sugammadex.

Incorrect Answers:
Answer 1: Bupivacaine is a local anesthetic that functions by blocking voltage-gated sodium channels in nerves. Local anesthetics is typically not reversed; however, phentolamine mesylate could be used to decrease the duration of effect.

Answer 2: Ketamine is a dissociative agent that functions as an NMDA antagonist in the central nervous system. There is no widely used reversal agent so overdose should be treated with supportive care.

Answer 3: Propofol is a sedative agent that functions by potentiating GABA A channels in the central nervous system. The acetylcholinesterase inhibitor physostigmine can be used as a reversal agent.

Answer 4: Succinylcholine is an AChR agonist that functions through depolarizing blockade. This is the opposite of the mechanism of the autoantibodies produced in myasthenia gravis.

Bullet Summary:
Patients with myasthenia gravis are particularly sensitive to the effect of non-depolarizing acetylcholine receptor blockers such as vecuronium.

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