Muscle physiology: malignant hyperthermia: practice question

A Physiology 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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Physiology · Muscle physiology: malignant hyperthermia

Sample item

A 22-year-old man undergoing general anaesthesia with halothane and succinylcholine develops muscle rigidity, tachycardia, rising end-tidal carbon dioxide and a temperature of 40 degrees C. Which drug directly treats the underlying defect?

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

The answer and the reasoning

D. Dantrolene, which blocks calcium release through the ryanodine receptor

Malignant hyperthermia is a pharmacogenetic disorder, usually of the RYR1 gene, in which volatile anaesthetics and succinylcholine trigger uncontrolled calcium release from the sarcoplasmic reticulum. Sustained contraction produces heat, acidosis and hypercarbia. Dantrolene inhibits the ryanodine receptor, and the triggering agents must be stopped with active cooling.

Option by option

  • A. Propranolol, which blocks beta-adrenergic stimulation of the heart

    Beta-blockade may slow the heart rate but does not correct the muscle defect.

  • B. Paracetamol, which resets the hypothalamic temperature set point

    Antipyretics act through the hypothalamus and are ineffective, since the heat arises from muscle.

  • C. Neostigmine, which increases acetylcholine at the end plate

    Neostigmine would increase cholinergic stimulation and does not address calcium release.

  • D. Dantrolene, which blocks calcium release through the ryanodine receptor (correct)

    Dantrolene blocks the ryanodine receptor and stops the calcium release.

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.

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Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is D, Dantrolene, which blocks calcium release through the ryanodine receptor. Malignant hyperthermia is a pharmacogenetic disorder, usually of the RYR1 gene, in which volatile anaesthetics and succinylcholine trigger uncontrolled calcium release from the sarcoplasmic reticulum.

Why is "Propranolol, which blocks beta-adrenergic stimulation of the heart" not the answer?

Beta-blockade may slow the heart rate but does not correct the muscle defect.

Why is "Paracetamol, which resets the hypothalamic temperature set point" not the answer?

Antipyretics act through the hypothalamus and are ineffective, since the heat arises from muscle.

Why is "Neostigmine, which increases acetylcholine at the end plate" not the answer?

Neostigmine would increase cholinergic stimulation and does not address calcium release.

What concept does this question test?

It tests Muscle physiology: malignant hyperthermia in Physiology. Sustained contraction produces heat, acidosis and hypercarbia. Dantrolene inhibits the ryanodine receptor, and the triggering agents must be stopped with active cooling.

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 physiology: malignant hyperthermia?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology 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.