Intravenous and inhalational agents: dexmedetomidine loading bolus: 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 · Intravenous and inhalational agents: dexmedetomidine loading bolus

Sample item

A rapid loading bolus of dexmedetomidine causes a brief rise in blood pressure followed by hypotension and bradycardia. What explains the biphasic response?

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

The answer and the reasoning

A. Peripheral alpha-2B vasoconstriction first, then central sympatholysis

A rapid bolus of dexmedetomidine stimulates peripheral alpha-2B receptors on vascular smooth muscle, causing transient vasoconstriction and hypertension. Central alpha-2A action then reduces sympathetic outflow, producing hypotension and bradycardia. A slow loading infusion limits the first phase.

Option by option

  • A. Peripheral alpha-2B vasoconstriction first, then central sympatholysis (correct)

    Correct. Peripheral vasoconstriction comes first and central sympatholysis follows.

  • B. Histamine release followed by vagal block

    Dexmedetomidine is not a histamine releaser and has no vagal blocking action.

  • C. Direct cholinergic stimulation followed by ganglion blockade

    Dexmedetomidine does not act at cholinergic receptors or ganglia.

  • D. Beta-receptor stimulation followed by beta blockade

    Dexmedetomidine does not act on beta receptors.

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 A, Peripheral alpha-2B vasoconstriction first, then central sympatholysis. A rapid bolus of dexmedetomidine stimulates peripheral alpha-2B receptors on vascular smooth muscle, causing transient vasoconstriction and hypertension.

Why is "Histamine release followed by vagal block" not the answer?

Dexmedetomidine is not a histamine releaser and has no vagal blocking action.

Why is "Direct cholinergic stimulation followed by ganglion blockade" not the answer?

Dexmedetomidine does not act at cholinergic receptors or ganglia.

Why is "Beta-receptor stimulation followed by beta blockade" not the answer?

Dexmedetomidine does not act on beta receptors.

What concept does this question test?

It tests Intravenous and inhalational agents: dexmedetomidine loading bolus in Anaesthesia. Central alpha-2A action then reduces sympathetic outflow, producing hypotension and bradycardia. A slow loading infusion limits the first phase.

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 Intravenous and inhalational agents: dexmedetomidine loading bolus?

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.