Most reactions to iodinated or gadolinium contrast are mild: a few hives, itching, nausea. They need observation and perhaps an antihistamine. The moment a reaction involves a second system — wheeze, stridor, hoarseness, hypotension, or diffuse spreading urticaria with any of these — it is anaphylaxis, and intramuscular adrenaline is the first drug, not the last. Delay in giving it is the commonest error in managing contrast anaphylaxis.
- Give adrenaline IM into the anterolateral thigh for any contrast reaction involving airway, breathing or circulation: 0.5 mg (0.5 mL of 1 mg/mL) in adults, 0.01 mg/kg (maximum 0.5 mg) in children.
- Repeat after 5 minutes if there is no improvement.
- Lay a hypotensive patient flat with legs raised and give rapid IV fluid.
- Keep a pre-drawn or labelled adrenaline ampoule and a dosing card in every contrast room.
- Document the agent and reaction clearly so the next department sees it.
Why it matters
Radiology rooms see anaphylaxis rarely enough that hesitation, not the reaction, is often what causes harm.
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