Asphyxia: freshwater versus seawater: 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 · Asphyxia: freshwater versus seawater

Sample item

In classical experimental teaching, which sequence follows aspiration of a large volume of freshwater into the lungs?

ARapid absorption, haemodilution, haemolysis, hyperkalaemia and ventricular fibrillationBHaemoconcentration, hypernatraemia and pulmonary oedema from fluid drawn into the alveoliCMetabolic alkalosis, hypokalaemia and bradycardiaDHypovolaemic shock from fluid loss into the gut

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

The answer and the reasoning

A. Rapid absorption, haemodilution, haemolysis, hyperkalaemia and ventricular fibrillation

Hypotonic freshwater crosses the alveolar membrane into the circulation, causing hypervolaemia and haemodilution. Red cell lysis releases potassium, and hyperkalaemia with hypoxia leads to ventricular fibrillation. Hypertonic seawater instead draws plasma into the alveoli, so haemoconcentration and pulmonary oedema result.

Option by option

A. Rapid absorption, haemodilution, haemolysis, hyperkalaemia and ventricular fibrillation (correct)
Correct. This is the classical freshwater sequence.
B. Haemoconcentration, hypernatraemia and pulmonary oedema from fluid drawn into the alveoli
This describes seawater drowning, where hypertonic fluid draws plasma into the lungs.
C. Metabolic alkalosis, hypokalaemia and bradycardia
This is not the pattern; freshwater causes hyperkalaemia, not hypokalaemia.
D. Hypovolaemic shock from fluid loss into the gut
Fluid is absorbed from the lungs rather than lost into the gut.

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.

Questions about this Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is A, Rapid absorption, haemodilution, haemolysis, hyperkalaemia and ventricular fibrillation. Hypotonic freshwater crosses the alveolar membrane into the circulation, causing hypervolaemia and haemodilution.

Why is "Haemoconcentration, hypernatraemia and pulmonary oedema from fluid dr…" not the answer?

This describes seawater drowning, where hypertonic fluid draws plasma into the lungs.

Why is "Metabolic alkalosis, hypokalaemia and bradycardia" not the answer?

This is not the pattern; freshwater causes hyperkalaemia, not hypokalaemia.

Why is "Hypovolaemic shock from fluid loss into the gut" not the answer?

Fluid is absorbed from the lungs rather than lost into the gut.

What concept does this question test?

It tests Asphyxia: freshwater versus seawater in Forensic Medicine. Red cell lysis releases potassium, and hyperkalaemia with hypoxia leads to ventricular fibrillation. Hypertonic seawater instead draws plasma into the alveoli, so haemoconcentration and pulmonary oedema result.

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 Asphyxia: freshwater versus seawater?

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.