Muscle relaxants: resistance after major burns: practice question

A Anaesthesia question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Anaesthesia · Muscle relaxants: resistance after major burns

Sample item

A man three weeks after 40 percent burns needs much larger and more frequent doses of atracurium than a healthy patient to maintain paralysis. Which change best explains this?

AInhibition of plasma cholinesterase by burn productsBReduced release of acetylcholine from the motor nerve endingCLower muscle blood flow slowing drug delivery to the endplateDProliferation of extrajunctional acetylcholine receptors

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. Proliferation of extrajunctional acetylcholine receptors

After a major burn the muscle membrane expresses many extrajunctional receptors, so more non-depolarising drug is needed to occupy enough receptors. The same change makes suxamethonium dangerous because of potassium release. Resistance begins about a week after injury and persists for months.

Option by option

A. Inhibition of plasma cholinesterase by burn products
Atracurium does not depend on plasma cholinesterase, and inhibition would not cause resistance.
B. Reduced release of acetylcholine from the motor nerve ending
Less acetylcholine released would make the patient more sensitive, not resistant.
C. Lower muscle blood flow slowing drug delivery to the endplate
Reduced blood flow would delay onset but would not raise the dose requirement for maintenance.
D. Proliferation of extrajunctional acetylcholine receptors (correct)
Correct. Extra receptors mean more drug is needed to block the same fraction, so resistance results.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is D, Proliferation of extrajunctional acetylcholine receptors. After a major burn the muscle membrane expresses many extrajunctional receptors, so more non-depolarising drug is needed to occupy enough receptors.

Why is "Inhibition of plasma cholinesterase by burn products" not the answer?

Atracurium does not depend on plasma cholinesterase, and inhibition would not cause resistance.

Why is "Reduced release of acetylcholine from the motor nerve ending" not the answer?

Less acetylcholine released would make the patient more sensitive, not resistant.

Why is "Lower muscle blood flow slowing drug delivery to the endplate" not the answer?

Reduced blood flow would delay onset but would not raise the dose requirement for maintenance.

What concept does this question test?

It tests Muscle relaxants: resistance after major burns in Anaesthesia. The same change makes suxamethonium dangerous because of potassium release. Resistance begins about a week after injury and persists for months.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Muscle relaxants: resistance after major burns?

Make a table of each agent, its key advantage and its main side effect. Then use the flashcards and the other Anaesthesia questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.