Inhalational 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 · Inhalational agents

Sample item

At the end of a long anaesthetic with nitrous oxide, the patient is breathing room air, becomes drowsy and cyanosed and the saturation falls. This is best explained by:

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

The answer and the reasoning

D. Diffusion hypoxia

When nitrous oxide is stopped, large volumes diffuse rapidly from blood into the alveoli and dilute alveolar oxygen and carbon dioxide. This causes diffusion hypoxia, prevented by giving 100% oxygen for 5 to 10 minutes after discontinuation.

Option by option

  • A. Absorption atelectasis

    Absorption atelectasis occurs when high oxygen concentrations are used, not during nitrous oxide washout.

  • B. Second gas effect

    The second gas effect speeds up induction and concerns uptake, not recovery hypoxia.

  • C. Malignant hyperthermia

    Malignant hyperthermia would show hypercarbia, rigidity and a rising temperature.

  • D. Diffusion hypoxia (correct)

    Correct. Rapid outpouring of nitrous oxide dilutes alveolar oxygen.

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, Diffusion hypoxia. When nitrous oxide is stopped, large volumes diffuse rapidly from blood into the alveoli and dilute alveolar oxygen and carbon dioxide.

Why is "Absorption atelectasis" not the answer?

Absorption atelectasis occurs when high oxygen concentrations are used, not during nitrous oxide washout.

Why is "Second gas effect" not the answer?

The second gas effect speeds up induction and concerns uptake, not recovery hypoxia.

Why is "Malignant hyperthermia" not the answer?

Malignant hyperthermia would show hypercarbia, rigidity and a rising temperature.

What concept does this question test?

It tests Inhalational agents in Anaesthesia. This causes diffusion hypoxia, prevented by giving 100% oxygen for 5 to 10 minutes after discontinuation.

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 Inhalational 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.