Perioperative Anaphylaxis

Recognition: bronchospasm, unexplained hypotension, tachycardia, urticaria or flushing, angioedema. Anaphylaxis may occur without skin signs under general anesthesia. Cardiovascular collapse may be the sole presenting feature.

Remove or stop the likely trigger. Common perioperative triggers include antibiotics, neuromuscular blocking agents (NMBAs), latex, chlorhexidine, colloids, blood products, and dyes.

Call for help. Inform the surgeon of the emergency. Request anaphylaxis drug box if separate from standard emergency drugs.

Epinephrine IV: Adult 50 mcg bolus (0.5 mL of 1:10,000 dilution), repeat every 1-2 minutes as needed. Start infusion at 0.05-0.1 mcg/kg/min for refractory hypotension. Pediatric: 1 mcg/kg IV.

Administer 100% oxygen. Secure the airway early if angioedema is progressing -- intubation may become impossible if delayed.

Volume resuscitation: crystalloid 20-40 mL/kg IV bolus. Adults may require 4-8 liters due to massive vasodilation and capillary leak.

Secondary treatments: hydrocortisone 200 mg IV (does not treat acute phase, prevents biphasic reaction), chlorphenamine or cetirizine as antihistamine, salbutamol (albuterol) nebulized or IV for persistent bronchospasm, vasopressin 2 units IV for refractory hypotension.

Timed mast cell tryptase blood draws: first sample as soon as possible after treatment initiated, second at 1-2 hours after onset, third at 24+ hours or at follow-up (baseline level).

Observe for 6-12 hours for biphasic reaction (recurrence of symptoms without re-exposure). Admit patient and refer to allergy clinic for formal investigation.

Document the suspected trigger, timing of exposure and symptom onset, treatments given, and tryptase results. Report to institutional adverse event reporting system.