Key Points
- Use the highest‑yield diagnostic test early; do not let testing delay time‑critical therapy.
- Set objective targets and reassess frequently.
- Plan definitive source control or disease‑specific therapy when indicated; document follow‑up and patient education.
Algorithm
- Immediate IM epinephrine; call for help; airway/oxygen/IV access and fluids.
- Add adjuncts after epi; treat bronchospasm with inhaled β-agonists.
- Observe 4–6 h (longer if severe/biphasic risk); discharge with autoinjector and anaphylaxis plan; refer to allergy.
Clinical Synopsis & Reasoning
Acute, life-threatening allergic reaction with airway, breathing, or circulatory compromise. Give IM epinephrine 0.3–0.5 mg (1 mg/mL) in the lateral thigh immediately and repeat every 5–15 minutes as needed. Position patient supine, provide high-flow oxygen and IV fluids; add adjuncts after epinephrine.
Treatment Strategy & Disposition
Stabilize ABCs. Initiate guideline‑concordant first‑line therapy with precise dosing and continuous monitoring. Escalate to advanced/procedural interventions based on explicit failure criteria. Define ICU, step‑down, and ward disposition triggers; involve specialty teams early.
Epidemiology / Risk Factors
- Risk varies by comorbidity and precipitants; see citations for condition‑specific data.
Investigations
| Test | Role / Rationale | Typical Findings | Notes |
|---|
| Clinical criteria (skin/mucosa + respiratory or circulatory compromise) | Diagnosis | Do not delay treatment | — |
| ECG and continuous monitoring | Safety | Detect arrhythmias | — |
| Serum tryptase (optional, early) | Support | Helps confirm severe anaphylaxis | Not for acute decisions |
High-Risk & Disposition Triggers
| Trigger | Why it matters | Action |
|---|
| Airway edema/stridor/hoarseness | Impending obstruction | Prepare for difficult airway; early intubation |
| Hypotension or refractory bronchospasm | Shock | Repeat IM epi; IV infusion; ICU |
| Beta-blocker therapy | Epi resistance | Use glucagon infusion |
| Biphasic reaction risk (severe case) | Recurrence | Observe ≥6–24 h based on severity |
| Remote location or poor follow-up | Safety | Longer observation; education and autoinjector |
Pharmacology
| Medication/Intervention | Mechanism | Onset | Role in Therapy | Limitations |
|---|
| Epinephrine 0.3–0.5 mg IM (1 mg/mL) q5–15 min | Adrenergic agonist | Immediate | First-line, life-saving | IV infusion if refractory |
| Normal saline boluses (20 mL/kg) | Resuscitation | Minutes | Counter distributive shock | — |
| H1/H2 blockers and corticosteroids (adjunct) | Symptom control | Hours | Urticaria/relapse prevention (limited evidence) | Do not replace epinephrine |
| Glucagon for patients on β-blockers (1–5 mg IV bolus → infusion) | Bypass β blockade | Minutes | Refractory hypotension/bronchospasm | Nausea/vomiting common |
Prognosis / Complications
- Outcome depends on timeliness of diagnosis and definitive therapy; monitor for complications.
Patient Education / Counseling
- Provide red‑flag education, adherence guidance, and explicit return precautions; arrange timely specialty follow‑up.
References
- WAO/AAAAI anaphylaxis guidelines — Link