Emergency medicine: severe hyponatraemia: 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.

Try it

General Medicine · Emergency medicine: severe hyponatraemia

Sample item

A 34-year-old woman drank large volumes of water during a marathon. She develops headache and vomiting followed by a generalised seizure. Serum sodium is 118 mmol/L. What is the most appropriate immediate treatment?

AOral tolvaptanBA bolus of 100 to 150 mL of 3% saline intravenously, repeated if symptoms persistCRapid correction to 135 mmol/L within 6 hoursDFluid restriction alone

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

The answer and the reasoning

B. A bolus of 100 to 150 mL of 3% saline intravenously, repeated if symptoms persist

Seizure from acute hyponatraemia indicates cerebral oedema and needs urgent hypertonic saline, which quickly raises sodium by about 4 to 6 mmol/L and reverses herniation risk. After this, the total rise is limited to no more than 8 to 10 mmol/L in 24 hours to avoid osmotic demyelination, particularly if hyponatraemia is chronic. Fluid restriction suits mild asymptomatic cases.

Option by option

A. Oral tolvaptan
Tolvaptan is slow, risks overcorrection and is not for emergencies.
B. A bolus of 100 to 150 mL of 3% saline intravenously, repeated if symptoms persist (correct)
Correct. Hypertonic saline reduces brain swelling quickly in symptomatic hyponatraemia.
C. Rapid correction to 135 mmol/L within 6 hours
Correcting to normal that fast risks osmotic demyelination, so the rise must be capped.
D. Fluid restriction alone
Restriction acts too slowly for a seizing patient with cerebral oedema.

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 General Medicine question

What is the answer to this General Medicine question?

The best answer is B, A bolus of 100 to 150 mL of 3% saline intravenously, repeated if symptoms persist. Seizure from acute hyponatraemia indicates cerebral oedema and needs urgent hypertonic saline, which quickly raises sodium by about 4 to 6 mmol/L and reverses herniation risk.

Why is "Oral tolvaptan" not the answer?

Tolvaptan is slow, risks overcorrection and is not for emergencies.

Why is "Rapid correction to 135 mmol/L within 6 hours" not the answer?

Correcting to normal that fast risks osmotic demyelination, so the rise must be capped.

Why is "Fluid restriction alone" not the answer?

Restriction acts too slowly for a seizing patient with cerebral oedema.

What concept does this question test?

It tests Emergency medicine: severe hyponatraemia in General Medicine. After this, the total rise is limited to no more than 8 to 10 mmol/L in 24 hours to avoid osmotic demyelination, particularly if hyponatraemia is chronic. Fluid restriction suits mild asymptomatic cases.

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 Emergency medicine: severe hyponatraemia?

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.