Toxicology: barium carbonate poisoning: 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 · Toxicology: barium carbonate poisoning

Sample item

A man ingests barium carbonate rat poison and has vomiting, diarrhoea, progressive flaccid weakness and U waves on the ECG. Which laboratory abnormality is responsible for the weakness?

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

The answer and the reasoning

C. Severe hypokalaemia

Barium blocks potassium channels in the cell membrane, so potassium cannot leave cells and a large shift occurs from the plasma into cells. The resulting hypokalaemia causes flaccid paralysis and arrhythmias. Treatment is intravenous potassium replacement with monitoring, and sodium or magnesium sulphate may precipitate the soluble barium.

Option by option

  • A. Severe hyperkalaemia

    Hyperkalaemia would cause peaked T waves, not U waves.

  • B. Hypocalcaemia

    Hypocalcaemia causes tetany and a long QT interval rather than flaccid paralysis with U waves.

  • C. Severe hypokalaemia (correct)

    Correct. Barium traps potassium inside the cells, causing profound hypokalaemia.

  • D. Hyponatraemia

    Hyponatraemia does not explain the ECG changes and flaccid paralysis.

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 C, Severe hypokalaemia. Barium blocks potassium channels in the cell membrane, so potassium cannot leave cells and a large shift occurs from the plasma into cells.

Why is "Severe hyperkalaemia" not the answer?

Hyperkalaemia would cause peaked T waves, not U waves.

Why is "Hypocalcaemia" not the answer?

Hypocalcaemia causes tetany and a long QT interval rather than flaccid paralysis with U waves.

Why is "Hyponatraemia" not the answer?

Hyponatraemia does not explain the ECG changes and flaccid paralysis.

What concept does this question test?

It tests Toxicology: barium carbonate poisoning in Forensic Medicine. The resulting hypokalaemia causes flaccid paralysis and arrhythmias. Treatment is intravenous potassium replacement with monitoring, and sodium or magnesium sulphate may precipitate the soluble barium.

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 Toxicology: barium carbonate poisoning?

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.