Key Points
- Use the highest‑yield diagnostic test early; do not let testing delay time‑critical therapy.
- Set objective targets (hemodynamic, neurologic, respiratory) and reassess frequently.
- Plan definitive source control or reperfusion when indicated; document follow‑up and patient education.
Algorithm
- Recognize clinical anaphylaxis; call for help; place on monitor; supine with legs elevated.
- Give IM epinephrine in lateral thigh; repeat q5–15 min if needed.
- Provide high‑flow oxygen and large‑volume IV fluids for hypotension.
- Add H1/H2 blockers and corticosteroids as adjuncts; consider inhaled β‑agonist for bronchospasm.
- Observe 4–6 h (longer if severe/asthma/beta‑blockers); discharge with auto‑injector and emergency action plan.
- Refer to Allergy/Immunology for trigger evaluation and avoidance strategies.
Clinical Synopsis & Reasoning
Treat rapidly with IM epinephrine in the lateral thigh; repeat every 5–15 min as needed. Add oxygen, IV fluids, H1/H2 blockers, and corticosteroids as adjuncts; observe for biphasic reactions and prescribe an epinephrine auto‑injector with an action plan.
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 diagnosis | Syndrome recognition | Acute skin/mucosal + respiratory or hypotension | Diagnosis is clinical; do not delay Epi |
| Serum tryptase (adjunct) | Supports diagnosis | Peak 1–2 h post‑onset | Not required for treatment |
| Allergy referral | Prevention | Identify triggers | Education & auto‑injector training |
Pharmacology
| Medication/Intervention | Mechanism | Onset | Role in Therapy | Limitations |
|---|---|---|---|---|
| Epinephrine 0.3–0.5 mg IM (1 mg/mL) q5–15 min | α/β agonist | Minutes | First‑line life‑saving therapy | Use 0.01 mg/kg in children; no absolute contraindications |
| Normal saline bolus | Crystalloid | Minutes | Hypotension/poor perfusion | Large volumes may be needed |
| Diphenhydramine ± famotidine | H1/H2 blockers | Hours | Symptom control (adjunct) | Sedation; do not replace Epi |
| Methylprednisolone | Glucocorticoid | Hours | Adjunct; prevents protracted symptoms | Evidence mixed for biphasic prevention |
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.