Electrolytes: hypokalaemia: 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 · Electrolytes: hypokalaemia

Sample item

A 35-year-old woman with persistent vomiting has serum potassium of 2.6 mmol/L and metabolic alkalosis. Which ECG changes are most likely?

AST depression, flattened T waves and prominent U wavesBProlonged QT from long ST segmentCShortened QT interval with ST elevationDTall peaked T waves and widened QRS

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

The answer and the reasoning

A. ST depression, flattened T waves and prominent U waves

Hypokalaemia delays ventricular repolarisation, causing ST depression, T wave flattening and prominent U waves, with risk of ventricular arrhythmias such as torsades de pointes. Peaked T waves occur in hyperkalaemia. Vomiting causes loss of hydrogen and potassium and renal potassium wasting.

Option by option

A. ST depression, flattened T waves and prominent U waves (correct)
Correct. U waves with flat T waves are the classic hypokalaemia pattern.
B. Prolonged QT from long ST segment
A prolonged ST segment with long QT is typical of hypocalcaemia.
C. Shortened QT interval with ST elevation
A short QT is seen in hypercalcaemia.
D. Tall peaked T waves and widened QRS
Peaked T waves and a wide QRS indicate hyperkalaemia.

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 Biochemistry question

What is the answer to this Biochemistry question?

The best answer is A, ST depression, flattened T waves and prominent U waves. Hypokalaemia delays ventricular repolarisation, causing ST depression, T wave flattening and prominent U waves, with risk of ventricular arrhythmias such as torsades de pointes.

Why is "Prolonged QT from long ST segment" not the answer?

A prolonged ST segment with long QT is typical of hypocalcaemia.

Why is "Shortened QT interval with ST elevation" not the answer?

A short QT is seen in hypercalcaemia.

Why is "Tall peaked T waves and widened QRS" not the answer?

Peaked T waves and a wide QRS indicate hyperkalaemia.

What concept does this question test?

It tests Electrolytes: hypokalaemia in Biochemistry. Peaked T waves occur in hyperkalaemia. Vomiting causes loss of hydrogen and potassium and renal potassium wasting.

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 Electrolytes: hypokalaemia?

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.