Local and regional anaesthesia: pruritus with intrathecal morphine: 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 · Local and regional anaesthesia: pruritus with intrathecal morphine

Sample item

A woman given intrathecal morphine for caesarean delivery develops intense facial itching two hours later, with no rash and stable blood pressure. Which treatment is appropriate?

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

The answer and the reasoning

B. Low-dose naloxone, nalbuphine or ondansetron

Pruritus is the commonest side effect of neuraxial opioids and is mediated by mu receptor effects, not histamine. It responds to low-dose naloxone, nalbuphine or ondansetron, while antihistamines mainly cause sedation.

Option by option

  • A. Subcutaneous adrenaline as for anaphylaxis

    Adrenaline is not needed in the absence of anaphylaxis.

  • B. Low-dose naloxone, nalbuphine or ondansetron (correct)

    Correct. These agents treat opioid-mediated pruritus.

  • C. Intravenous hydrocortisone for an allergic reaction

    There is no sign of allergy, so steroids are not indicated.

  • D. Intravenous chlorpheniramine as first-line therapy for histamine release

    The itch is not histamine mediated, so antihistamines are of little benefit.

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 B, Low-dose naloxone, nalbuphine or ondansetron. Pruritus is the commonest side effect of neuraxial opioids and is mediated by mu receptor effects, not histamine.

Why is "Subcutaneous adrenaline as for anaphylaxis" not the answer?

Adrenaline is not needed in the absence of anaphylaxis.

Why is "Intravenous hydrocortisone for an allergic reaction" not the answer?

There is no sign of allergy, so steroids are not indicated.

Why is "Intravenous chlorpheniramine as first-line therapy for histamine rele…" not the answer?

The itch is not histamine mediated, so antihistamines are of little benefit.

What concept does this question test?

It tests Local and regional anaesthesia: pruritus with intrathecal morphine in Anaesthesia. It responds to low-dose naloxone, nalbuphine or ondansetron, while antihistamines mainly cause sedation.

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 Local and regional anaesthesia: pruritus with intrathecal morphine?

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.