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Critical Care / ICU · Ward Pathways · Locked — free with a referral
By Dr Javed Akhtar · Last reviewed 2 October 2026
Presentation Urticaria + stridor + BP 78/40 minutes after IV antibiotic — this is adrenaline IM now, not antihistamines first.
Red flags Hoarseness, tongue or lip swelling Stridor or silent chest SBP <90 or collapse Trigger was parenteral (IV drug, sting) — faster and deadlier Differential diagnosis Vasovagal syncope (bradycardia, no skin signs) ACE-inhibitor angioedema (no urticaria, bradykinin — adrenaline less effective) Scombroid poisoning Panic attack / globus When to admit, call ICU or discharge Admit: All who needed adrenaline infusion, 2+ doses, or had airway involvementObserve: Minimum 6 h from symptom resolution; 12–24 h if severe/asthma/β-blockerICU: Refractory shock, airway compromise, infusion requiredKey points IM anterolateral thigh — fastest absorption, safest route; no maximum cumulative dose in true anaphylaxis Glucagon 1–5 mg IV for patients on β-blockers with refractory anaphylaxis Biphasic reactions occur in up to 20% — observation is treatment Never Give adrenaline IV bolus in a monitored, non-arrest patient — IM thigh first (IV bolus = arrhythmia/infarction) Treat with antihistamines or steroids while delaying adrenaline Discharge early or without an adrenaline auto-injector and allergy referral Common mistakes Walking the patient to resus — lay them flat immediately Underdosing adrenaline in adults (0.3 mg is paediatric thinking) Relying on steroids to 'prevent' biphasic reactions No auto-injector training before discharge Disposition and follow-up Discharge with 2 adrenaline auto-injectors, written action plan, trigger avoidance advice, and allergy/immunology referral for testing in 4–6 weeks.
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