Perioperative Anaphylaxis, Management & Culprit Workup

Acute management and post-event allergy workup of suspected perioperative (peri-anaesthetic) anaphylaxis. Covers immediate treatment (stop all potential triggers, epinephrine, timed tryptase), the role of acute/baseline tryptase (20%+2 rule), and systematic culprit identification by skin testing and specific IgE, antibiotics, neuromuscular blocking agents, chlorhexidine, dyes, and latex are the leading culprits (NAP6).

Evidence tier: Guideline-derived.

Decision points

Acute event now, or post-event allergy workup?
Was serial tryptase elevated by the 20%+2 rule?

Do-not-miss pitfalls

Under anaesthesia the classic warning signs are masked, cardiovascular collapse, unexplained high airway pressures/bronchospasm, or desaturation may be the FIRST sign. Cutaneous signs are absent in a substantial minority. Maintain a low threshold to declare anaphylaxis.
Stop ALL potential triggers, not just the obvious one, chlorhexidine (line/gel/coated devices), patent blue dye, colloids, and latex are frequently overlooked culprits because they are not "drugs" given by the anaesthetist.
Tryptase must be TIMED, an acute sample at ~1-2 h plus a baseline ≥24 h later (or convalescent). A single random level is hard to interpret. Apply the 20% + 2 rule (acute > 1.2 × baseline + 2 ng/mL).
A normal acute tryptase does NOT exclude anaphylaxis, it is frequently normal in milder or non-mast-cell reactions. Do not let a normal tryptase stop the culprit workup when the event was clinically convincing.
Every perioperative anaphylaxis must be referred for specialist culprit identification, relabeling or guessing the culprit risks a fatal re-exposure at the next anaesthetic. "Avoid all the drugs given" is not an acceptable substitute for identifying the actual agent.
Skin testing is done 4-6 weeks after the event, testing too early (during the refractory period) risks false negatives. Use validated non-irritant concentrations to avoid false positives.
Neuromuscular blocking agents cross-react, a patient allergic to one NMBA may react to others (especially the aminosteroids rocuronium/vecuronium). Test the whole class to find a safe alternative; do not assume another NMBA is safe.
Chlorhexidine anaphylaxis is rising and easily missed, it is in skin preps, lubricant gels, and impregnated central venous catheters. Specifically test for it, and document chlorhexidine-free requirements.

Evidence & citations

Clinician decision support. Verify against the cited source. Not a substitute for clinical judgment. 100% on-device; no patient data is stored or transmitted.