Spinal anesthesia: physiology: 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 · Spinal anesthesia: physiology

Sample item

After spinal anesthesia for a lower-limb procedure, a patient becomes hypotensive and nauseated. What is the principal mechanism?

AIncreased systemic vascular resistanceBDirect opioid-induced histamine releaseCHyperventilation-induced alkalosisDSympathetic blockade causing vasodilation and reduced venous return

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

The answer and the reasoning

D. Sympathetic blockade causing vasodilation and reduced venous return

Spinal anesthesia blocks sympathetic outflow below the level of the block, producing venodilation and reduced systemic vascular resistance. The resulting fall in venous return and blood pressure can cause nausea.

Option by option

A. Increased systemic vascular resistance
Systemic vascular resistance generally falls rather than rises.
B. Direct opioid-induced histamine release
No opioid is required for this mechanism.
C. Hyperventilation-induced alkalosis
Hyperventilation is not the primary explanation for this predictable regional-anesthetic effect.
D. Sympathetic blockade causing vasodilation and reduced venous return (correct)
Correct. Sympathectomy is the principal cause of early spinal hypotension.

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 Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is D, Sympathetic blockade causing vasodilation and reduced venous return. Spinal anesthesia blocks sympathetic outflow below the level of the block, producing venodilation and reduced systemic vascular resistance.

Why is "Increased systemic vascular resistance" not the answer?

Systemic vascular resistance generally falls rather than rises.

Why is "Direct opioid-induced histamine release" not the answer?

No opioid is required for this mechanism.

Why is "Hyperventilation-induced alkalosis" not the answer?

Hyperventilation is not the primary explanation for this predictable regional-anesthetic effect.

What concept does this question test?

It tests Spinal anesthesia: physiology in Anaesthesia. The resulting fall in venous return and blood pressure can cause nausea.

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 Spinal anesthesia: physiology?

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.