Asphyxial deaths: fresh water drowning physiology: practice question

A Forensic Medicine 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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Forensic Medicine · Asphyxial deaths: fresh water drowning physiology

Sample item

A child is retrieved from a freshwater well after drowning. Which sequence best explains death in this child?

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

The answer and the reasoning

A. Hypotonic water crosses alveoli, causing haemodilution, haemolysis and hyperkalaemia, leading to ventricular fibrillation

Fresh water is hypotonic and is rapidly absorbed through the alveolar membrane into the circulation. The resulting hypervolaemia and haemodilution cause red cell haemolysis, release of potassium and hypoxia, so ventricular fibrillation is a common mechanism, with death in about 4 to 5 minutes. Sea water has the opposite osmotic effect.

Option by option

  • A. Hypotonic water crosses alveoli, causing haemodilution, haemolysis and hyperkalaemia, leading to ventricular fibrillation (correct)

    Correct. Absorption, haemolysis and hyperkalaemia precipitate fibrillation.

  • B. Cold-induced vagal arrest without inhalation

    Vagal arrest does not depend on inhaling water and is a separate mechanism.

  • C. Laryngospasm without water inhalation causes slow asphyxia

    Laryngospasm without inhalation is dry drowning, which has little water in the lungs.

  • D. Hypertonic water draws plasma into alveoli, causing haemoconcentration

    Haemoconcentration is a feature of hypertonic sea water drowning.

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 Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is A, Hypotonic water crosses alveoli, causing haemodilution, haemolysis and hyperkalaemia, leading to ventricular fibrillation. Fresh water is hypotonic and is rapidly absorbed through the alveolar membrane into the circulation.

Why is "Cold-induced vagal arrest without inhalation" not the answer?

Vagal arrest does not depend on inhaling water and is a separate mechanism.

Why is "Laryngospasm without water inhalation causes slow asphyxia" not the answer?

Laryngospasm without inhalation is dry drowning, which has little water in the lungs.

Why is "Hypertonic water draws plasma into alveoli, causing haemoconcentration" not the answer?

Haemoconcentration is a feature of hypertonic sea water drowning.

What concept does this question test?

It tests Asphyxial deaths: fresh water drowning physiology in Forensic Medicine. The resulting hypervolaemia and haemodilution cause red cell haemolysis, release of potassium and hypoxia, so ventricular fibrillation is a common mechanism, with death in about 4 to 5 minutes. Sea water has the opposite osmotic effect.

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 Asphyxial deaths: fresh water drowning physiology?

Learn postmortem changes with their timelines, and toxicology as poison, sign, test and antidote. Then use the flashcards and the other Forensic Medicine 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.