Anaphylaxis Management
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Direct answer
Anaphylaxis is a rapidly progressive multisystem allergic reaction — airway swelling, bronchospasm, circulatory collapse, often skin signs — and its entire treatment hangs on one drug given one way: adrenaline 0.01 mg per kilogram intramuscularly as a 1:1000 solution, maximum 0.5 mg in adults, into the anterolateral thigh, repeated every five minutes if the response is inadequate. The patient is laid flat with legs raised (sitting up has caused deaths from empty-ventricle collapse), oxygen and crystalloid support the circulation, and antihistamines or steroids are adjuncts only — never substitutes. Every patient is observed for a biphasic recurrence, commonly for at least 6 to 12 hours after resolution, and leaves with an autoinjector plan and a referral thought.
What you must remember
- Diagnostic constellation: acute onset of skin or mucosal involvement plus respiratory compromise or hypotension, OR two or more systems rapidly after an allergen exposure, OR known allergy with hypotension after a likely trigger — any one pathway satisfies the clinical diagnosis.
- Adrenaline, the numbers: 0.01 mg/kg of 1:1000 (1 mg/mL) intramuscularly, anterolateral thigh — adults 0.5 mg, repeated every 5 minutes as needed; a 1 mL ampoule equals 1 mg, the arithmetic every trolley must own.
- Position rule: supine with legs elevated; pregnancy tilts the uterus left; breathing difficulty may permit sitting, but sudden standing or sitting upright in a collapsing patient is dangerous.
- Refractory pathway: adrenaline infusion in a monitored setting, plus generous crystalloid (large volumes may be needed — allergic vasodilation behaves like distributive shock), intubation early if stridor escalates.
- Second-line only after adrenaline: nebulised salbutamol for bronchospasm, an antihistamine for urticaria, hydrocortisone per local practice — none of them abort the reaction and none justifies delaying the injection.
- Biphasic reaction: recurrence up to 72 hours later in a minority, most within the first 12 — the reason observation for at least 6-12 hours is standard, longer for severe or refractory presentations.
- Common Indian triggers: drugs (antibiotics, NSAIDs, contrast), stings, foods (nuts, seafood) — and a documented reaction earns a written allergy record, alert bracelet advice and an adrenaline autoinjector prescription where available.
Ten minutes after a penicillin injection
A 28-year-old receives his first dose of an antibiotic in the outpatient department and returns to the nursing station nine minutes later with diffuse hives, a tight throat and a whistling chest. He is laid flat with legs raised while someone calls the resuscitation team; pulse 118 and thready, pressure 84/50, saturation 93 per cent. Adrenaline 0.5 mg is drawn from the 1 mg ampoule — one ampoule, one mL, an easy arithmetic under pressure — and injected into the outer thigh, massaged lightly. High-flow oxygen goes on and two cannulae are secured; a 500 mL crystalloid bolus follows because the pressure has not moved by the two-minute mark. At five minutes the urticaria is fading, the voice clears, and the pressure reads 102/64 — no second dose needed. Chlorpheniramine and hydrocortisone follow as written adjuncts. He is observed for eight hours because of the laryngeal involvement, discharged with a documented allergy entry and an autoinjector plan. The entire successful episode used one ampoule of adrenaline, correctly early, correctly intramuscular — the two decisions that change outcome in this disease.
Where students slip
The best-built MCQ trap offers the route: intravenous adrenaline at 1:1000 concentration, or subcutaneous administration, or the antihistamine-first option — the answer is intramuscular into the thigh, and intravenous use is reserved for monitored refractory cases. The second slip is sequence: steroids act in hours and cannot abort a reaction unfolding in minutes; examiners reward the candidate who explicitly demotes them. The third is the observation question — discharging a resolved patient at two hours ignores the biphasic risk that standard guidance manages with 6-12 hour observation. Indian viva angles include the scarcity of autoinjectors and the counselling that substitutes — avoidance lists, written action plans, family teaching of ampoule-and-syringe dosing — and the field reality that the 108 ambulance often carries the first adrenaline the patient ever meets.
Frequently asked questions
What is the first-line dose of adrenaline in adult anaphylaxis?
0.5 mg of 1:1000 solution intramuscularly into the anterolateral thigh, repeated every five minutes if needed — weight-based at 0.01 mg/kg, capped at 0.5 mg.
Why is the patient laid flat with legs raised?
Anaphylactic vasodilation pools blood peripherally; the supine position with legs raised preserves venous return — sudden upright posture has caused fatal empty-heart arrests.
What role do antihistamines and steroids play?
Adjunct relief for skin symptoms and possible help against the biphasic phase — they never replace adrenaline and never justify delaying the injection.
How long is an anaphylaxis patient observed after recovery?
Commonly 6 to 12 hours minimum, longer after severe, refractory or laryngeal presentations, because a biphasic recurrence can appear without re-exposure.
Which findings indicate impending airway compromise?
Hoarseness, stridor, tongue or lip swelling and a changing voice — signals to escalate monitoring and prepare for early intubation rather than wait and watch.