Muscle relaxants: suxamethonium hyperkalaemia: 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: suxamethonium hyperkalaemia

Sample item

A patient with 30% burns sustained 10 days ago needs urgent debridement. Why should suxamethonium be avoided?

AIt is ineffective in burnsBIt causes malignant hyperthermia alwaysCIt causes severe bradycardia onlyDUpregulated extrajunctional receptors cause massive potassium release

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

The answer and the reasoning

D. Upregulated extrajunctional receptors cause massive potassium release

After burns, denervation and immobilisation, acetylcholine receptors proliferate across the muscle membrane, and depolarisation then releases large potassium loads that can cause cardiac arrest. The risk begins about 24 to 48 hours after injury and lasts for months.

Option by option

A. It is ineffective in burns
It remains effective in burns.
B. It causes malignant hyperthermia always
It does not always cause MH.
C. It causes severe bradycardia only
Bradycardia is a separate effect.
D. Upregulated extrajunctional receptors cause massive potassium release (correct)
Correct. Extrajunctional receptors cause hyperkalaemia.

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, Upregulated extrajunctional receptors cause massive potassium release. After burns, denervation and immobilisation, acetylcholine receptors proliferate across the muscle membrane, and depolarisation then releases large potassium loads that can cause cardiac arrest.

Why is "It is ineffective in burns" not the answer?

It remains effective in burns.

Why is "It causes malignant hyperthermia always" not the answer?

It does not always cause MH.

Why is "It causes severe bradycardia only" not the answer?

Bradycardia is a separate effect.

What concept does this question test?

It tests Muscle relaxants: suxamethonium hyperkalaemia in Anaesthesia. The risk begins about 24 to 48 hours after injury and lasts 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: suxamethonium hyperkalaemia?

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.