Clinical biochemistry: potassium disorders: practice question

A Biochemistry 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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Biochemistry · Clinical biochemistry: potassium disorders

Sample item

A man with chronic kidney disease has serum potassium 7.2 mmol/L and an ECG showing peaked T waves with a widened QRS. Which intervention should be given first to protect the heart?

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

The answer and the reasoning

B. Intravenous calcium gluconate

Calcium raises the threshold potential of cardiac myocytes and restores the gap between resting and threshold potentials, so it stabilises the membrane within minutes. It does not lower serum potassium. Insulin with glucose and beta-agonists then shift potassium into cells, and removal is achieved with binders, diuretics or dialysis.

Option by option

  • A. Nebulised salbutamol

    Salbutamol shifts potassium into cells but is an adjunct and acts more slowly.

  • B. Intravenous calcium gluconate (correct)

    Correct. Calcium gluconate gives immediate membrane stabilisation when ECG changes are present.

  • C. Oral patiromer

    Patiromer removes potassium over hours to days and has no immediate cardioprotective effect.

  • D. Insulin with dextrose

    Insulin with dextrose shifts potassium into cells but takes longer and does not stabilise the membrane directly.

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 Biochemistry question

What is the answer to this Biochemistry question?

The best answer is B, Intravenous calcium gluconate. Calcium raises the threshold potential of cardiac myocytes and restores the gap between resting and threshold potentials, so it stabilises the membrane within minutes.

Why is "Nebulised salbutamol" not the answer?

Salbutamol shifts potassium into cells but is an adjunct and acts more slowly.

Why is "Oral patiromer" not the answer?

Patiromer removes potassium over hours to days and has no immediate cardioprotective effect.

Why is "Insulin with dextrose" not the answer?

Insulin with dextrose shifts potassium into cells but takes longer and does not stabilise the membrane directly.

What concept does this question test?

It tests Clinical biochemistry: potassium disorders in Biochemistry. It does not lower serum potassium. Insulin with glucose and beta-agonists then shift potassium into cells, and removal is achieved with binders, diuretics or dialysis.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 Clinical biochemistry: potassium disorders?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry 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.