A 28-year-old woman presents to the emergency department 15 minutes after eating peanuts at a restaurant. She complains of severe pruritus, angioedema of the lips and tongue, and stridor. Her blood pressure is 92/58 mmHg and heart rate is 128/min. She has no prior history of anaphylaxis. What is the most appropriate immediate next step in management?

Explanation

## Immediate Management of Anaphylaxis **Key Point:** Anaphylaxis is a medical emergency requiring immediate epinephrine administration — delay is dangerous and increases mortality. ### Clinical Recognition This patient exhibits classic signs of anaphylaxis: - Onset within 15 minutes of allergen exposure - Cutaneous: pruritus, angioedema - Airway: stridor (laryngeal edema) - Cardiovascular: hypotension (92/58), tachycardia (128/min) - Known trigger: peanut ingestion ### Why Epinephrine Is First-Line **High-Yield:** Epinephrine is the ONLY drug that addresses the pathophysiology of anaphylaxis: - **α-adrenergic effects:** vasoconstriction → reverses hypotension, reduces angioedema - **β-adrenergic effects:** bronchodilation, increased cardiac contractility, inhibits mast cell degranulation **Clinical Pearl:** The anterolateral thigh is the preferred site because: - Faster and more reliable absorption than arm or gluteal sites - Easier to administer in emergency settings - Intramuscular route ensures rapid onset (5–15 minutes) ### Dose and Timing - **Dose:** 0.3–0.5 mg of 1:1000 epinephrine IM for adults - **Timing:** Administer IMMEDIATELY — do not wait for IV access, investigations, or observation - **Repeat:** May repeat every 5–15 minutes if symptoms persist or recur ### Subsequent Steps (After Epinephrine) Once epinephrine is given: 1. Establish IV access 2. Administer IV fluids (normal saline bolus) 3. Give antihistamines (IV diphenhydramine) and corticosteroids (IV hydrocortisone or methylprednisolone) — these are **adjuncts**, not primary therapy 4. Observe for biphasic reactions (4–12 hours) 5. Discharge with epinephrine auto-injector prescription **Mnemonic:** **AEIOU** for anaphylaxis management: - **A**irway (assess and secure) - **E**pinephrine (IM, immediate) - **I**V access - **O**xygen (if hypoxic) - **U**pright position (legs elevated if hypotensive) **Warning:** ~~Corticosteroids or antihistamines alone~~ are NOT sufficient for anaphylaxis — they do not reverse the acute cardiovascular collapse or airway compromise. They are used as adjuncts AFTER epinephrine.