Electrolytes: practice question

A General 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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General Medicine · Electrolytes

Sample item

A smoker with a lung mass has serum sodium 124 mmol/L and appears euvolaemic. Urine osmolality is high and urine sodium is raised. He has mild headache only. What is the most appropriate initial management?

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

The answer and the reasoning

D. Fluid restriction

A low plasma sodium with inappropriately concentrated urine in a euvolaemic patient with small cell lung cancer suggests SIADH. Mild chronic cases are treated with fluid restriction, while hypertonic saline is reserved for severe symptoms such as seizures or coma, with slow correction.

Option by option

  • A. Rapid 3% saline bolus to normalise sodium

    Rapid hypertonic correction risks osmotic demyelination and is not needed for mild symptoms.

  • B. Desmopressin

    Desmopressin increases water retention and would worsen the hyponatraemia.

  • C. Infusion of isotonic saline

    Isotonic saline can worsen hyponatraemia in SIADH because the solute is excreted in concentrated urine while the water is retained.

  • D. Fluid restriction (correct)

    Correct. Restricting water intake corrects dilution in SIADH.

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 General Medicine question

What is the answer to this General Medicine question?

The best answer is D, Fluid restriction. A low plasma sodium with inappropriately concentrated urine in a euvolaemic patient with small cell lung cancer suggests SIADH.

Why is "Rapid 3% saline bolus to normalise sodium" not the answer?

Rapid hypertonic correction risks osmotic demyelination and is not needed for mild symptoms.

Why is "Desmopressin" not the answer?

Desmopressin increases water retention and would worsen the hyponatraemia.

Why is "Infusion of isotonic saline" not the answer?

Isotonic saline can worsen hyponatraemia in SIADH because the solute is excreted in concentrated urine while the water is retained.

What concept does this question test?

It tests Electrolytes in General Medicine. Mild chronic cases are treated with fluid restriction, while hypertonic saline is reserved for severe symptoms such as seizures or coma, with slow correction.

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 Electrolytes?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General 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.