Special anaesthesia: tetralogy of Fallot spell: 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 · Special anaesthesia: tetralogy of Fallot spell

Sample item

A child with tetralogy of Fallot develops sudden deep cyanosis, falling saturation and hyperpnoea under anaesthesia. Which drug is most appropriate along with 100% oxygen and fluid?

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

The answer and the reasoning

D. Phenylephrine

During a hypercyanotic spell, infundibular spasm and a fall in systemic vascular resistance increase right-to-left shunting. Phenylephrine raises systemic resistance and reduces the shunt, and volume, oxygen, deepening anaesthesia and beta blockade also help. Beta agonists increase infundibular spasm and tachycardia.

Option by option

  • A. Isoprenaline

    Isoprenaline causes tachycardia and vasodilation, which worsen the spell.

  • B. Salbutamol

    Salbutamol vasodilates systemically and can increase the shunt.

  • C. Dobutamine

    Dobutamine increases contractility and infundibular spasm.

  • D. Phenylephrine (correct)

    Correct. Raising systemic vascular resistance reduces right-to-left flow across the ventricular septal defect.

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 D, Phenylephrine. During a hypercyanotic spell, infundibular spasm and a fall in systemic vascular resistance increase right-to-left shunting.

Why is "Isoprenaline" not the answer?

Isoprenaline causes tachycardia and vasodilation, which worsen the spell.

Why is "Salbutamol" not the answer?

Salbutamol vasodilates systemically and can increase the shunt.

Why is "Dobutamine" not the answer?

Dobutamine increases contractility and infundibular spasm.

What concept does this question test?

It tests Special anaesthesia: tetralogy of Fallot spell in Anaesthesia. Phenylephrine raises systemic resistance and reduces the shunt, and volume, oxygen, deepening anaesthesia and beta blockade also help. Beta agonists increase infundibular spasm and tachycardia.

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 Special anaesthesia: tetralogy of Fallot spell?

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.