Nerve and muscle: succinylcholine versus rocuronium: 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.

Try it

Physiology · Nerve and muscle: succinylcholine versus rocuronium

Sample item

Two patients undergo surgery. One receives rocuronium and the other succinylcholine. On a train-of-four test, which finding distinguishes the early block produced by succinylcholine?

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

The answer and the reasoning

B. Reduced twitch height with no fade

Depolarising blockers produce a phase I block with reduced but equal twitch heights (no fade) and no post-tetanic potentiation. Non-depolarising blockers such as rocuronium cause fade on train-of-four and tetanic stimulation, with post-tetanic potentiation.

Option by option

  • A. Complete loss of response with no recovery

    A complete loss without recovery is not the typical pattern of either drug.

  • B. Reduced twitch height with no fade (correct)

    Correct. A phase I depolarising block shows lower twitches without fade.

  • C. Marked fade with potentiation after tetanus

    Fade with post-tetanic potentiation characterises non-depolarising blockers.

  • D. Increasing twitch height with each stimulus

    Increasing twitch height with repetition suggests an increment such as in Lambert-Eaton syndrome.

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.

More Physiology questions

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is B, Reduced twitch height with no fade. Depolarising blockers produce a phase I block with reduced but equal twitch heights (no fade) and no post-tetanic potentiation.

Why is "Complete loss of response with no recovery" not the answer?

A complete loss without recovery is not the typical pattern of either drug.

Why is "Marked fade with potentiation after tetanus" not the answer?

Fade with post-tetanic potentiation characterises non-depolarising blockers.

Why is "Increasing twitch height with each stimulus" not the answer?

Increasing twitch height with repetition suggests an increment such as in Lambert-Eaton syndrome.

What concept does this question test?

It tests Nerve and muscle: succinylcholine versus rocuronium in Physiology. Non-depolarising blockers such as rocuronium cause fade on train-of-four and tetanic stimulation, with post-tetanic potentiation.

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 Nerve and muscle: succinylcholine versus rocuronium?

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.