NBME 20 Succinylcholine (NBME Answers)

NBME 20 Answers

nbme20/Block 3/Question#47 (reveal difficulty score)
A 60-year-old woman has prolonged apnea ...
Succinylcholine 🔍 / 📺 / 🌳 / 📖
tags:

+12 upvote downvote
submitted by ∗xxabi(293)

get full access to all content ⋅ pick a username

The duration of action of Succinylcholine is determined by its metabolism by plasma cholinesterase. So if there is abnormal plasma cholinesterase (=psuedocholinesterase), it will lead to delayed metabolism of succinylcholine as well as mivacirum, heroin, and cocaine.

get full access to all content ⋅ pick a username

athenathefirst So because there was a problem with cholinesterase then the only one would be affected is acetylcholine since it's metabolized by acetylcholine. +

athenathefirst *acetylcholine esterase (sorry meant that) +

+6 upvote downvote
submitted by ∗niboonsh(409)

get full access to all content ⋅ pick a username

https://www.youtube.com/watch?v=WGWFFN01qkA succinylcholine usually has v fast duration of action bcuz metabolized by plasma pseudocholinesterase. With atypical pseudocholinesterase, decreased metabolism of succinylcholine and thus causes a prolonged duration of action of succinylcholine ----> APNEA

get full access to all content ⋅ pick a username

chandlerbas i love that mosquito and then SLAP +1

+1 upvote downvote
submitted by ∗haozhier(23)

get full access to all content ⋅ pick a username

From FA, succinylcholine can be reversed during phase 2 by cholinesterase inhibitor. Can someone explain if succinylcholine is metabolized by cholinesterase, how can we use cholinesterase inhibitors to reverse it?

get full access to all content ⋅ pick a username

roseanneg I think what happens is that acetylcholinesterase inhibitors will start to increase acetylcholine in the synapse and that can now compete with succinylcholine. But then again, at phase 2, it says that there is desensitization to acetylcholine at phase II so idk. Also, note that succinylcholine is metabolized by PLASMA cholinesterase but is resistant to acetylcholinesterase. I'm not sure if that contributes to the reason. +

+0 upvote downvote
submitted by thomas(3)

get full access to all content ⋅ pick a username

Not sure about this, but it seems to me that this is referring to "pseudocholinesterase inhibitor deficiency. It's an enzyme defect that is triggered by NMJ blockers - succinylcholine or curare's.

https://en.wikipedia.org/wiki/Pseudocholinesterase_deficiency

get full access to all content ⋅ pick a username

usmleuser007 I believe this question was stating that AchE activity was abnormal = it was not lowering the Ach activity. Which suggests that another ligand like Ach was being used. +

Must-See Comments from nbme20

amorah on Cytomegalovirus infection
masonkingcobra on Contact with parakeets
hayayah on Capillary hydrostatic: increased; ...
hayayah on X chromosome-linked isoenzymes
medbitch94 on Mannose 6-phosphate
hello on Capillary hydrostatic: increased; ...
hayayah on Osteoblasts
imgdoc on Hypophosphatemia
hayayah on Missense
celeste on 50%
justgettinby on Omeprazole
andrewk1 on Cold, dry air
yotsubato on Jugular venous pressure of 12 mm Hg
strugglebus on Drug effect