Synopsis
Recognise anaphylaxis from rapidly developing airway, breathing or circulatory compromise, administer prompt intramuscular adrenaline, and plan risk-based observation and allergy follow-up.
- Anaphylaxis is a clinical diagnosis; skin changes may be absent in severe reactions.
- Give adult adrenaline 500 micrograms IM using 0.5 mL of 1 mg/mL solution.
- Repeat IM adrenaline after five minutes when airway, breathing or circulation compromise persists.
Key red flags
Stridor, severe bronchospasm, collapse or persistent hypotension after an allergen exposure requires immediate IM adrenaline and resuscitation support.
Investigation priorities
Determine severity and judge the immediate treatment response.
Management branches
Rapidly developing airway, breathing or circulation problems make anaphylaxis the working diagnosis.
- Stop the suspected trigger when feasible, call help and give 500 micrograms IM adrenaline into the anterolateral thigh without waiting for venous access.
- Position safely, provide oxygen and airway support, attach monitoring and obtain IV access; give rapid crystalloid for hypotension, shock or poor initial response.
Airway swelling has resolved, breathing has normalised and blood pressure and heart rate are stable.
Key medicines
Adrenaline for adult anaphylaxisGive 500 micrograms IM, equal to 0.5 mL of 1 mg/mL adrenaline, into the anterolateral thigh; repeat after 5 minutes if airway, breathing or circulation problems persist.Check concentration and route explicitly. Avoid routine IV bolus adrenaline in a patient with a circulation; use specialist titrated IV treatment for refractory reactions.
Non-glucose isotonic crystalloidFor adult hypotension, shock or poor response to adrenaline, give a rapid 500–1,000 mL IV bolus and reassess; further fluid is guided by perfusion and tolerance.Fluids complement adrenaline and must not delay repeat dosing. Monitor for overload and avoid a suspected causative colloid preparation.