Anaphylaxis

Key points

• Adrenaline IM into the anterolateral mid-thigh is the single most important treatment — give it immediately and REPEAT every 5 minutes if there is no improvement in airway, breathing or circulation.
• Adrenaline doses (1 in 1,000): under 6 months 100-150 micrograms · 6 months to 6 years 150 micrograms · 6-12 years 300 micrograms · adult and over 12 years 500 micrograms · most adult auto-injectors deliver only 300 micrograms, so draw up from an ampoule where possible for a second dose.
• CORTICOSTEROIDS (hydrocortisone) ARE NO LONGER RECOMMENDED for the routine emergency treatment of anaphylaxis — benefit is doubtful and they may be harmful in children. This is a change from the older algorithm.
• ANTIHISTAMINES (chlorphenamine) are now THIRD-LINE and only for cutaneous symptoms — they must never delay or replace adrenaline.
• Give a rapid IV crystalloid bolus (adult 500-1000 ml; child 10 ml/kg) · lie the patient flat with legs raised, or semi-recumbent if breathing is easier, and do NOT sit or stand them up suddenly — this can cause cardiac arrest.
• REFRACTORY anaphylaxis = persisting respiratory or cardiovascular symptoms despite TWO appropriate doses of IM adrenaline → follow the refractory algorithm: seek expert help, start an adrenaline infusion, give further fluids. Corticosteroids may be considered only after initial resuscitation, never in preference to adrenaline and fluids.
• Mast cell tryptase: take as soon as possible after treatment, a second sample 1-2 hours after symptom onset, and a baseline at follow-up · observe for 6-12 hours depending on severity and risk factors · refer to a specialist allergy service and prescribe two adrenaline auto-injectors with training.

Decision points in this pathway

• Improvement in airway, breathing and circulation after 5 minutes?
• Still no improvement after TWO appropriate doses of IM adrenaline?

The full step-by-step algorithm, including what to do at each branch, opens in the app for approved members.