← Diagnosis and Management Guides
Anaphylaxis
Key considerations: Anaphylactic shock, Angioedema with airway compromise
Cannot miss
- Anaphylactic shock
- Angioedema with airway compromise
Likely diagnoses
- Drug-induced anaphylaxis
- Food allergy
- Insect sting
- Idiopathic anaphylaxis
Red flags
- Stridor
- Wheezing
- Hypotension
- Altered mental status
Workup
- history: Allergen exposure, timing, prior reactions, medications; exam: Airway assessment, urticaria, angioedema, wheezing, BP; labs: Tryptase level (peaks 1-2hr after onset); imaging: Not typically needed acutely; bedside: Continuous monitoring
Management
- immediate: IM epinephrine 0.3-0.5mg (1:1000) anterolateral thigh — FIRST and MOST IMPORTANT; Repeat q5-15min if needed; IV fluids for hypotension; general: Adjuncts: diphenhydramine 50mg IV, ranitidine 50mg IV, methylprednisolone 125mg IV; Observe 4-6 hours for biphasic reaction; Prescribe epinephrine auto-injector at discharge
Disposition
- admit: Severe reaction, hypotension requiring multiple epi doses, ongoing symptoms; discharge: After 4-6hr observation if resolved, with EpiPen and allergy referral; consults: Allergy/immunology for follow-up
Clinical pearls
- Epinephrine is the ONLY first-line treatment — do NOT delay for antihistamines or steroids
- Biphasic reactions occur in up to 20% of cases, typically within 8-12 hours
Source and review
- WAO Anaphylaxis Guidelines 2020. Last reviewed: 2024-11-01