Paediatric anaesthesia: pyloric stenosis: practice question

A Anaesthesia 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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Anaesthesia · Paediatric anaesthesia: pyloric stenosis

Sample item

An infant with pyloric stenosis has repeated vomiting. Which metabolic derangement is expected, and when should surgery be done?

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

The answer and the reasoning

C. Hypochloraemic hypokalaemic metabolic alkalosis, after correction

Vomiting of gastric acid causes loss of hydrogen and chloride, with compensatory renal loss of potassium. Pyloromyotomy is a medical rather than a surgical emergency, so fluids and electrolytes are corrected first.

Option by option

  • A. Hyperchloraemic acidosis, immediately

    Acidosis does not occur from gastric loss.

  • B. Hyperkalaemic acidosis, immediately

    Potassium is low, not high.

  • C. Hypochloraemic hypokalaemic metabolic alkalosis, after correction (correct)

    Correct. This is the characteristic picture.

  • D. Respiratory alkalosis, after correction

    The disturbance is metabolic, not respiratory.

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 Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is C, Hypochloraemic hypokalaemic metabolic alkalosis, after correction. Vomiting of gastric acid causes loss of hydrogen and chloride, with compensatory renal loss of potassium.

Why is "Hyperchloraemic acidosis, immediately" not the answer?

Acidosis does not occur from gastric loss.

Why is "Hyperkalaemic acidosis, immediately" not the answer?

Potassium is low, not high.

Why is "Respiratory alkalosis, after correction" not the answer?

The disturbance is metabolic, not respiratory.

What concept does this question test?

It tests Paediatric anaesthesia: pyloric stenosis in Anaesthesia. Pyloromyotomy is a medical rather than a surgical emergency, so fluids and electrolytes are corrected first.

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 Paediatric anaesthesia: pyloric stenosis?

Make a table of each agent, its key advantage and its main side effect. Then use the flashcards and the other Anaesthesia 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.