Monitoring: evoked potentials and volatile agents: 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 · Monitoring: evoked potentials and volatile agents

Sample item

Which effect do volatile anaesthetics have on somatosensory and motor evoked potential monitoring during spinal surgery?

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

The answer and the reasoning

D. They reduce amplitude and increase latency in a dose-dependent manner, motor potentials being most sensitive

Volatile agents depress cortical evoked potentials, with an increase in latency and fall in amplitude, and motor evoked potentials are the most sensitive. For reliable monitoring, a technique based on total intravenous anaesthesia, low-dose volatile agent (below 0.5 MAC) and avoidance of neuromuscular blockers is used. Nitrous oxide also depresses amplitude.

Option by option

  • A. They enhance all potentials

    Potentials are not enhanced.

  • B. They affect only brainstem auditory potentials

    Cortical potentials are affected most, and brainstem potentials are the most resistant.

  • C. They have no effect

    Depression of potentials is well established.

  • D. They reduce amplitude and increase latency in a dose-dependent manner, motor potentials being most sensitive (correct)

    Correct. Volatile agents depress amplitude and prolong latency.

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, They reduce amplitude and increase latency in a dose-dependent manner, motor potentials being most sensitive. Volatile agents depress cortical evoked potentials, with an increase in latency and fall in amplitude, and motor evoked potentials are the most sensitive.

Why is "They enhance all potentials" not the answer?

Potentials are not enhanced.

Why is "They affect only brainstem auditory potentials" not the answer?

Cortical potentials are affected most, and brainstem potentials are the most resistant.

Why is "They have no effect" not the answer?

Depression of potentials is well established.

What concept does this question test?

It tests Monitoring: evoked potentials and volatile agents in Anaesthesia. For reliable monitoring, a technique based on total intravenous anaesthesia, low-dose volatile agent (below 0.5 MAC) and avoidance of neuromuscular blockers is used. Nitrous oxide also depresses amplitude.

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 Monitoring: evoked potentials and volatile agents?

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.