Anaphylaxis — Written Clinical Reasoning

Model answer — Part A: bee sting with airway compromise

Recognise and state the diagnosis. Acute onset of skin involvement (urticaria) plus respiratory compromise (stridor, wheeze) and hypotension after a known trigger — this satisfies the NIAID/FAAN criteria and is grade 3 (severe) anaphylaxis; the stridor makes airway the first threat ^{[1] [2]}.

First drug, first dose, exact route. Immediate adrenaline 0.5 mg (0.5 mL of 1:1000) intramuscularly into the anterolateral thigh — before IV access, before any other drug. The intramuscular thigh route gives faster, higher peak levels than subcutaneous injection, and undiluted IV bolus adrenaline in a perfusing patient is dangerous ^{[1] [3]}.

Position and support. Lie him flat with legs elevated and do not allow standing or walking; high-flow oxygen; wide-bore IV access with monitoring; call for senior airway and ICU help early because tongue swelling with stridor can progress to a difficult intubation ^[2].

Repeat and fill. Repeat adrenaline every 5 minutes while airway, breathing or circulatory features persist; give rapid IV crystalloid, 1–2 litres in the adult, for the vasodilated, leaking circulation ^[1].

Second-line agents — named, dosed and demoted. An H1-antihistamine for cutaneous symptoms once resuscitation is underway; a corticosteroid on the biphasic rationale; nebulised salbutamol for residual bronchospasm. State explicitly that none of these treats the acute phase and none has adequate trial evidence — adrenaline is the treatment ^[7].