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Retired NBME 21 Answers

nbme21/Block 2/Question#2 (reveal difficulty score)
A 4-year-old girl is conscious but unable to ...
Pseudocholinesterase deficiency ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–
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 +13  upvote downvote
submitted by โˆ—haliburton(224)
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https://ghr.nlm.nih.gov/condition/pseudocholinesterase-deficiency

"People with pseudocholinesterase deficiency may not be able to move or breathe on their own for a few hours after [fast-acting drugs, such as succinylcholine and mivacurium] are administered.

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ragacha  THX +



 +7  upvote downvote
submitted by โˆ—powerfulgarbage(17)
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There was a uworld Q on this. The duration of action of Succinylcholine is determined by its metabolism by plasma cholinesterase. Some people are homozygous for an abnormal plasma cholinesterase, aka "pseudocholinesterase" or "butyrylcholinesterase" (BCHE). People with a homozygous BCHE mutation have delayed metabolism of succinylcholine, mivacurium, heroin, and cocaine.

In these patients, paralysis from succinylcholine can last for hours and you have to maintain them on mechanical ventilation until they can breath on their own

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lovebug  2019FA 538pg. +1



 +2  upvote downvote
submitted by โˆ—d_holles(218)
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Also, I think what is key is to realize that injuring CN X ('intraoperative CN X injury') does not lead to diaphragm paralysis, only phrenic nerve injury would do that.

amboss.com/us/CN+X+injury

Furthermore, the other options ('idiosyncratic rxn to sevoflurane' and 'ryanodine receptor defect') are for malignant hyperthermia, NOT unable to breath spontaneously.

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 +1  upvote downvote
submitted by โˆ—an_improved_me(91)
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Might be a dumb question but... Can patients normally breathin on their own if givne succinylcholine?

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trazobone  Yes! Normal people will have an adequate level of pseudocholinesterase to break down the succinylcholine and eventually cease its effects. But if your question is, will succinylcholine still inhibit breathing in a normal person, yes it will. It will work to paralyze muscles (like your diaphragm) in both a normal person and in someone with the pseudocholinesterase deficiency. The main issue is the ability to eventually break down the succinylcholine and come out of the paralysis +1



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