Anaphylaxis

• ~10% of all anesthetic complications; 3.4% mortality
• >90% of reactions within 3 min of trigger
• Faster onset = more severe course
• Multiple drugs given simultaneously → identifying the culprit is difficult
• Vasoactive mediator release → ↑ secretions, ↑ bronchial tone, ↑ capillary permeability, ↓ vascular tone

Anaphylaxis (IgE-mediated, type I hypersensitivity) - Prior sensitization required → antigen-specific IgE on mast cells / basophils - Re-exposure → IgE cross-linking → degranulation - Independent of dose

Anaphylactoid - Direct mast cell/basophil activation OR complement activation — non-IgE - Can occur on first exposure - Dose-dependent

Treatment is identical for both.

Can have variable presentations with some or all of these.

Top intraoperative triggers: - Neuromuscular blockers — > 50% of intraop anaphylaxis. Rocuronium incidence quoted 1/3,500 to 1/445,000. - Antibiotics — β-lactams (cephalosporins, penicillins) - Latex — second most common - Chlorhexidine (rising incidence) - Colloids: HES 6% > albumin - Sugammadex (~1/35,000) - Contrast agents - Blood products

Latex allergy — high risk: - Healthcare workers (frequent exposure) - Children with spina bifida (multiple urogenital procedures) - Tropical fruit allergy (banana, kiwi, avocado, mango, passion fruit, chestnut) - Multiple prior surgeries / catheterizations

1. STOP the offending antigen (NMBA, antibiotic, latex, colloid, blood, contrast)
2. Notify surgeon AND call for help
3. 100% FiO₂
4. Discontinue vasodilating agents (volatile, narcotic infusion); give midazolam/ketamine for amnesia if hypotensive
5. IV fluid bolus — 2–4 L or more (vasodilation, capillary leak)
6. EPINEPHRINE (α1 supports BP, β2 bronchodilates)
7. - 10–100 mcg IV bolus, escalate as needed
8. - Infusion 0.02–0.3 mcg/kg/min
9. - 0.3–0.5 mg IM anterolateral thigh if no IV, repeat q5–15 min
10. - ACLS doses (0.1–1 mg) for cardiovascular collapse
11. Vasopressin bolus or norepinephrine infusion if escalating
12. Treat bronchospasm with albuterol and epinephrine

• Intubate especially if angioedema
• Invasive monitoring: large-bore IVs, arterial line, CVC, foley
• After stable:
• H1 blocker: diphenhydramine 0.5–1 mg/kg IV
• H2 blocker: ranitidine (theoretical benefit; low harm)
• Steroid: hydrocortisone 200 mg IV or methylprednisolone 1–2 mg/kg — to ↓ airway edema and prevent biphasic recurrence

Diagnostics: - Tryptase: peaks at 30–60 min, draw at 1–2 h and 24 h - Refer to allergist for skin testing 4–6 weeks later

Document and notify the patient; MedicAlert; communicate findings to PCP and pharmacy.