Trauma and burns: cyanide poisoning in smoke inhalation: practice question

A General Surgery 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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General Surgery · Trauma and burns: cyanide poisoning in smoke inhalation

Sample item

A man is rescued unconscious from a closed-room fire. His pulse oximeter reads 98 percent, carboxyhaemoglobin is 8 percent, and arterial lactate is 12 mmol/L with severe metabolic acidosis. Which treatment is most appropriate in addition to 100 percent oxygen?

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

The answer and the reasoning

B. Intravenous hydroxocobalamin

Burning plastics release hydrogen cyanide, which blocks cytochrome oxidase and causes profound lactic acidosis despite good oxygen saturation. A low carboxyhaemoglobin does not explain coma. Hydroxocobalamin binds cyanide to form cyanocobalamin and is the antidote of choice in smoke inhalation.

Option by option

  • A. Intravenous methylene blue

    Methylene blue treats methaemoglobinaemia and is not an antidote for cyanide.

  • B. Intravenous hydroxocobalamin (correct)

    Correct. Hydroxocobalamin binds cyanide and is the preferred antidote in smoke inhalation.

  • C. Hyperbaric oxygen therapy

    Hyperbaric oxygen is for severe carbon monoxide poisoning, which is not the problem with a carboxyhaemoglobin of 8 percent.

  • D. Intravenous N-acetylcysteine

    N-acetylcysteine treats paracetamol overdose.

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 General Surgery questions

Questions about this General Surgery question

What is the answer to this General Surgery question?

The best answer is B, Intravenous hydroxocobalamin. Burning plastics release hydrogen cyanide, which blocks cytochrome oxidase and causes profound lactic acidosis despite good oxygen saturation.

Why is "Intravenous methylene blue" not the answer?

Methylene blue treats methaemoglobinaemia and is not an antidote for cyanide.

Why is "Hyperbaric oxygen therapy" not the answer?

Hyperbaric oxygen is for severe carbon monoxide poisoning, which is not the problem with a carboxyhaemoglobin of 8 percent.

Why is "Intravenous N-acetylcysteine" not the answer?

N-acetylcysteine treats paracetamol overdose.

What concept does this question test?

It tests Trauma and burns: cyanide poisoning in smoke inhalation in General Surgery. A low carboxyhaemoglobin does not explain coma. Hydroxocobalamin binds cyanide to form cyanocobalamin and is the antidote of choice in smoke inhalation.

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 Trauma and burns: cyanide poisoning in smoke inhalation?

Learn classic signs and eponyms alongside what they diagnose. Then use the flashcards and the other General Surgery 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.