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Stem
A 28-year-old man with a known peanut allergy presents to the emergency department 10 minutes after accidentally eating a peanut-containing cookie. He is flushed and anxious, with swelling of the lips and tongue, a harsh stridor, an expiratory wheeze, and a reproducible blood pressure of 78/45 mmHg with a heart rate of 128/min. He is drowsy but rousable. His past history includes asthma (on salbutamol and a low-dose inhaled corticosteroid) and hypertension treated with bisoprolol 5 mg daily. On arrival he feels faint and tries to sit up.
Questions
a) What is the diagnosis, and which bedside criteria confirm it? (2 marks)
The diagnosis is anaphylaxis. It is confirmed clinically by the NIAID/FAAN (2006) criteria: acute onset (minutes) with skin/mucosal involvement (lip and tongue angioedema, flushing) AND at least one of respiratory compromise (stridor, wheeze) OR reduced BP/associated end-organ dysfunction (hypotension 78/45, drowsiness) — fulfilling criterion 1. No laboratory test is required before starting treatment.
b) Outline your IMMEDIATE management in the first 5 minutes. (4 marks)
- Call for help — senior clinician, resuscitation team, anaesthetist.
- POSITION — lie him supine with legs elevated; do NOT let him sit up (empty vena cava syndrome causes asystolic arrest).
- Airway and Breathing — high-flow oxygen 15 L/min via a non-rebreather mask; assess for progression of laryngeal oedema and prepare for early intubation.
- IM ADRENALINE 0.5 mg (0.5 mL of 1:1000) into the anterolateral thigh (vastus lateralis) — the single most important intervention; repeat after 5 minutes if no response.
- IV access — two large-bore cannulae; give a 500 to 1000 mL bolus of 0.9 percent sodium chloride rapidly, repeated as guided by response.
- Remove residual allergen (clear the mouth); do NOT delay adrenaline for any adjunct.
c) After TWO doses of IM adrenaline he remains hypotensive and bradycardic. Why, and what specific drug is indicated, and at what dose? (2 marks)
He is taking bisoprolol (a beta-blocker), which attenuates the beta-1 and beta-2 effects of adrenaline, producing refractory hypotension and bradycardia. The drug of choice is glucagon 1 to 5 mg IV over 5 minutes, followed by an infusion of 5 to 15 micrograms/min titrated to response. Glucagon bypasses the beta-receptor and activates adenylate cyclase directly via its own Gs-protein-coupled receptor. Atropine 0.5 to 1 mg IV may be added for bradycardia. If still refractory, start an IV adrenaline infusion and involve critical care.
d) After full recovery, what is the recommended observation period and the discharge bundle? (2 marks)
Observe for at least 6 hours (UK Resuscitation Council / NICE) because of the biphasic reaction risk (up to 15 percent, typically within 10 hours); overnight admission is indicated here because he needed TWO adrenaline doses and is asthmatic and beta-blocked. Send an acute serum tryptase (immediately and at 1 to 2 h) and a baseline (24 h or clinic) sample. Discharge with: TWO adrenaline autoinjectors (demonstrated), a written anaphylaxis action plan, allergen-avoidance advice, oral cetirizine and a short course of prednisolone, MedicAlert identification, and an urgent allergy clinic referral (within 2 to 4 weeks) for skin-prick testing, component-resolved diagnostics (Ara h 2), and consideration of oral immunotherapy.