Anaes · Critical incidents
Anaphylaxis under anaesthesia
Also known as Perioperative anaphylaxis · Anaphylactic reaction · IgE-mediated anaphylaxis · NAP6 · Perioperative allergy
Exam-exhaustive perioperative anaphylaxis: NAP6 culprits (antibiotics, NMBAs, chlorhexidine, dyes), adrenaline IM/IV doses, dual pathology with asthma/bronchospasm, tryptase timing, differential of intraoperative collapse, and specialist allergy follow-up for ANZCA Final and equivalents.
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Red flags
- Sudden profound hypotension or arrest minutes after a drug is anaphylaxis until proven otherwise — give adrenaline; do not wait for a rash under the drapes.
- NAP6: adrenaline was often late and under-dosed — IV 50 microgram boluses, repeat, then infusion; IM 500 micrograms if no IV access.
- Antibiotics the most numerous NAP6 culprits (94 of 199), then NMBAs (65); teicoplanin caused 38% of antibiotic cases from 12% of exposures; chlorhexidine and patent blue are easy to miss.
- Three tryptase samples: as soon as practical, at 1–2 h peak, and baseline (≥24 h or clinic) — then specialist perioperative allergy referral.
- Refractory bronchospasm + shock: treat both pathways; asthma does not exclude anaphylaxis and can coexist.
Meet the patient
Two minutes after rocuronium and cefazolin, your patient's blood pressure is 50 over 20, the SpO2 is falling, and the peak airway pressure has jumped to 45. There is no rash you can see under the drapes. The question in front of you is immediate: is this anaphylaxis, and where is the adrenaline?[2]
Two ideas frame every perioperative collapse: unexplained hypotension or bronchospasm minutes after a drug is anaphylaxis unless a more likely cause exists, and adrenaline is the disease-modifying drug — not metaraminol, not a fluid challenge while you hunt for a rash. Treat the physiology first, prove the mechanism later.[5]
References6ShowHide
- [1]Harper NJN, Cook TM, Garcez T, et al. Anaesthesia, surgery, and life-threatening allergic reactions: management and outcomes in the 6th National Audit Project (NAP6) Br J Anaesth, 2018.PMID 29935569
- [2]Harper NJN, Cook TM, Garcez T, et al. Anaesthesia, surgery, and life-threatening allergic reactions: epidemiology and clinical features of perioperative anaphylaxis in the 6th National Audit Project (NAP6) Br J Anaesth, 2018.PMID 29935567
- [3]Marinho S, Kemp H, Cook TM, et al. Cross-sectional study of perioperative drug and allergen exposure in UK practice in 2016: the 6th National Audit Project (NAP6) Allergen Survey Br J Anaesth, 2018.PMID 29935566
- [4]Wang J, Lieberman JA, Wallace DV, et al. Anaphylaxis in Practice: A Guide to the 2023 Practice Parameter Update J Allergy Clin Immunol Pract, 2024.PMID 38944199
- [5]Harper NJ, et al. Suspected anaphylactic reactions associated with anaesthesia Anaesthesia, 2009.PMID 19143700
- [6]Dodd A, Hughes A, Sargant N, et al. Evidence update for the treatment of anaphylaxis Resuscitation, 2021.PMID 33895231