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].

Model answer — Part B: refractory anaphylaxis on beta-blockers

Frame it. Ongoing hypotension despite three IM adrenaline doses is refractory anaphylaxis; her beta-blocker is both worsening the reaction and blunting adrenaline's effect, which explains the paradoxical bradycardia [4] [5].

Escalation. Urgent ICU involvement and arterial-level monitoring; move from repeated boluses to a titrated adrenaline infusion; continue judicious crystalloid with reassessment; prepare for definitive airway management if any upper-airway feature emerges [1] [5].

The key pharmacology. Glucagon 1–5 mg IV bolus followed by an infusion at 5–15 micrograms per minute — it stimulates adenylate cyclase via its own receptor, bypassing the blocked beta-receptor; this is the specific antidote-answer for beta-blocked refractory anaphylaxis [4]. Add a second vasopressor (noradrenaline or vasopressin) if vasoplegia dominates [5].

Investigation. Acute serum tryptase within 1–2 hours of onset and a baseline after 24 hours, interpreted as a delta; document the reaction to contrast precisely for the radiology record [6].

Discharge. Observe overnight given severity and multi-dose requirement; discharge with two adrenaline autoinjectors and training, a written action plan, specialist allergy referral, and a medication review that explicitly weighs her beta-blocker indication against future reaction risk — a shared, documented decision [6].