Nephrology and electrolytes: saline-induced acidosis: 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 · Nephrology and electrolytes: saline-induced acidosis

Sample item

A 30-year-old receives 6 litres of 0.9% saline for resuscitation. Blood shows sodium 142 mmol/L, chloride 118 mmol/L, bicarbonate 16 mmol/L and pH 7.30. What explains this acid-base picture?

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

The answer and the reasoning

D. Hyperchloraemic acidosis from the chloride load

The anion gap is 142 minus 118 minus 16, which equals 8, so the acidosis has a normal gap. Large volumes of chloride-rich fluid dilute bicarbonate and add chloride, giving hyperchloraemic acidosis. Balanced crystalloids reduce this problem.

Option by option

  • A. Respiratory acidosis from hypoventilation

    Respiratory acidosis would raise bicarbonate, not lower it.

  • B. Lactic acidosis from persistent hypoperfusion

    Lactic acidosis would raise the anion gap, which is normal here.

  • C. Ketoacidosis from starvation

    Ketoacidosis would also raise the anion gap.

  • D. Hyperchloraemic acidosis from the chloride load (correct)

    Correct. A normal anion gap with high chloride after saline fits a hyperchloraemic acidosis.

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, Hyperchloraemic acidosis from the chloride load. The anion gap is 142 minus 118 minus 16, which equals 8, so the acidosis has a normal gap.

Why is "Respiratory acidosis from hypoventilation" not the answer?

Respiratory acidosis would raise bicarbonate, not lower it.

Why is "Lactic acidosis from persistent hypoperfusion" not the answer?

Lactic acidosis would raise the anion gap, which is normal here.

Why is "Ketoacidosis from starvation" not the answer?

Ketoacidosis would also raise the anion gap.

What concept does this question test?

It tests Nephrology and electrolytes: saline-induced acidosis in General Medicine. Large volumes of chloride-rich fluid dilute bicarbonate and add chloride, giving hyperchloraemic acidosis. Balanced crystalloids reduce this problem.

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 Nephrology and electrolytes: saline-induced acidosis?

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.