## Clinical Recognition This is a classic presentation of **Type I hypersensitivity (anaphylaxis)** triggered by penicillin: - Rapid onset (15 minutes post-exposure) - Urticaria + angioedema + airway involvement (stridor) - Hemodynamic compromise (hypotension, tachycardia) ## Immediate Management Algorithm ```mermaid flowchart TD A[Anaphylaxis suspected]:::outcome --> B{Airway/Breathing/Circulation compromised?}:::decision B -->|Yes| C[IM Epinephrine 0.3-0.5 mg 1:1000]:::action B -->|No| D[Still give IM Epinephrine if any systemic signs]:::action C --> E[Lay supine, elevate legs]:::action E --> F[IV access, fluid resuscitation]:::action F --> G[H1 blocker + corticosteroid]:::action G --> H[Observe 4-8 hours minimum]:::action ``` **Key Point:** Epinephrine is the first-line, life-saving drug in anaphylaxis. Delay increases mortality risk. **High-Yield:** The correct dose is **0.3–0.5 mg of 1:1000 epinephrine IM** (not IV, not subcutaneous). Repeat every 5–15 minutes if needed. **Clinical Pearl:** Antihistamines and corticosteroids are **adjunctive**, not primary. They do not replace epinephrine and should not delay its administration. **Warning:** Skin prick testing during acute anaphylaxis is contraindicated and dangerous. Testing is done only after full recovery, weeks later, if allergy confirmation is needed. ## Why Epinephrine Works | Mechanism | Effect | |-----------|--------| | α1-adrenergic | Vasoconstriction → ↑ BP, ↓ angioedema | | β2-adrenergic | Bronchodilation, ↓ mast cell degranulation | | β1-adrenergic | ↑ cardiac output, HR | **Mnemonic: ABCDE of Anaphylaxis Management** — **A**irway, **B**reathing, **C**irculation (Epinephrine first), **D**rugs (H1/H2/steroids second), **E**levate legs, **E**voke history. [cite:Harrison 21e Ch 317]
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.