## Management of Acute Diphtheria with Airway Compromise **Key Point:** Diphtheria antitoxin must be administered immediately on clinical suspicion—delaying treatment for culture confirmation increases mortality, especially in respiratory diphtheria. Antitoxin is most effective when given early (within 24–48 hours of symptom onset). ### Why Immediate Antitoxin Is Critical **High-Yield:** Diphtheria toxin is irreversibly bound to EF-2 within minutes of production. Antitoxin only neutralizes *circulating* (unbound) toxin; it does NOT reverse toxin already internalized into cells. Therefore, early administration is life-saving. 1. **Antitoxin efficacy decreases with time**: - Day 1–2: ~90% mortality reduction - Day 3–4: ~50% mortality reduction - Day 6+: Minimal benefit 2. **Respiratory diphtheria is a medical emergency**: - Risk of airway obstruction from pseudomembrane - Risk of myocarditis with sudden cardiovascular collapse - Mortality without antitoxin: 5–10% (respiratory) to 20% (with complications) ### Management Algorithm ```mermaid flowchart TD A[Clinical suspicion of diphtheria<br/>pseudomembrane + systemic toxicity]:::outcome A --> B[Administer antitoxin immediately<br/>Do NOT wait for culture/PCR]:::action B --> C[Airway assessment]:::decision C -->|Stridor/respiratory distress| D[Prepare for intubation<br/>ICU admission]:::action C -->|Stable airway| E[Supportive care<br/>Isolation]:::action B --> F[Send throat swab<br/>Culture + Elek test/PCR]:::action B --> G[Antibiotics<br/>Penicillin G or Erythromycin]:::action D --> H[Monitor for myocarditis<br/>ECG, cardiac enzymes]:::action E --> H ``` ### Antitoxin Administration - **Source**: Horse serum (equine antitoxin)—only source available - **Dose**: 20,000–100,000 units IV (depending on severity and duration) - **Route**: Intravenous preferred for rapid systemic distribution - **Risk**: Serum sickness (delayed hypersensitivity) in ~5–10% of recipients; anaphylaxis is rare (~0.1%) and manageable with epinephrine - **Contraindication to antitoxin**: None in diphtheria—benefit far outweighs anaphylaxis risk **Clinical Pearl:** Antitoxin is NOT contraindicated in respiratory diphtheria; it is indicated in ALL forms (respiratory, cutaneous, nasal, laryngeal). ### Concurrent Management 1. **Antibiotics**: Penicillin G (2 million units IV q4h) or Erythromycin (500 mg IV q6h) - Eradicate organism and prevent transmission - Do NOT replace antitoxin 2. **Airway management**: Intubation if stridor or respiratory distress 3. **Cardiac monitoring**: ECG, troponin; myocarditis is a major cause of death 4. **Isolation**: Respiratory precautions until 2 negative cultures post-treatment 5. **Vaccination**: Post-recovery, complete diphtheria vaccination series (toxoid-containing vaccine) **Mnemonic: ANTITOXIN ASAP = Antitoxin Neutralizes Toxin In circulation; Time Is critical; Obtain Xin (toxin confirmation) later; Antibiotics + Supportive care; Start immediately; Airway preparation; Post-recovery vaccination**
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