The single most important action in anaphylaxis is prompt intramuscular adrenaline, and delay is the factor most associated with fatal outcomes.
Give adrenaline intramuscularly into the anterolateral thigh as soon as anaphylaxis is recognised: do not wait for the reaction to progress, and do not reach first for antihistamines or steroids, which do not treat the airway, breathing or circulatory compromise. The adult dose is 0.5 mg (0.5 mL of 1 mg/mL) repeated after about 5 minutes if needed; paediatric doses are weight-based. Lay the patient flat with legs raised unless breathing is easier sitting up, give high-flow oxygen and intravenous fluids for hypotension, and only consider intravenous adrenaline infusion in refractory cases with monitoring.
The habit worth keeping is that intramuscular adrenaline is the treatment, given first and repeated, while antihistamines and steroids are at most adjuncts.
- Give intramuscular adrenaline into the anterolateral thigh as soon as anaphylaxis is recognised.
- Adult dose is 0.5 mg of 1 mg/mL, repeated after about 5 minutes if needed.
- Do not rely on antihistamines or steroids, which do not treat airway or circulatory compromise.
- Lay the patient flat with legs raised unless breathing is easier upright.
- Reserve intravenous adrenaline infusion for refractory cases with monitoring.
Why it matters
Delayed adrenaline, not its use, is what is associated with fatal anaphylaxis.
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