Muscle relaxants: diaphragm sensitivity: 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: diaphragm sensitivity

Sample item

While the adductor pollicis twitch is abolished after rocuronium, the patient coughs and moves the diaphragm when the tracheal tube touches the carina. What explains this?

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

The answer and the reasoning

D. The diaphragm is more resistant to non-depolarising block than the adductor pollicis

The diaphragm needs a higher dose of relaxant for block and recovers earlier than the adductor pollicis, so peripheral monitoring can overestimate depth at the airway. Patients may therefore cough while the thumb twitch is absent. Paralysis of peripheral muscles precedes the diaphragm.

Option by option

  • A. Rocuronium is rapidly metabolised in the thorax

    Rocuronium is eliminated by the liver and kidney, not in the thorax.

  • B. The diaphragm is more sensitive to block than the adductor pollicis

    If the diaphragm were more sensitive it would be paralysed before the thumb.

  • C. Cough is a smooth muscle reflex unaffected by relaxants

    Cough uses skeletal muscles that are affected by relaxants.

  • D. The diaphragm is more resistant to non-depolarising block than the adductor pollicis (correct)

    Correct. The diaphragm is more resistant than the adductor pollicis.

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 Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is D, The diaphragm is more resistant to non-depolarising block than the adductor pollicis. The diaphragm needs a higher dose of relaxant for block and recovers earlier than the adductor pollicis, so peripheral monitoring can overestimate depth at the airway.

Why is "Rocuronium is rapidly metabolised in the thorax" not the answer?

Rocuronium is eliminated by the liver and kidney, not in the thorax.

Why is "The diaphragm is more sensitive to block than the adductor pollicis" not the answer?

If the diaphragm were more sensitive it would be paralysed before the thumb.

Why is "Cough is a smooth muscle reflex unaffected by relaxants" not the answer?

Cough uses skeletal muscles that are affected by relaxants.

What concept does this question test?

It tests Muscle relaxants: diaphragm sensitivity in Anaesthesia. Patients may therefore cough while the thumb twitch is absent. Paralysis of peripheral muscles precedes the diaphragm.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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: diaphragm sensitivity?

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.