A 28-year-old woman with penetrating chest trauma and massive hemorrhage is in the emergency department. She is in Class IV hemorrhagic shock (BP undetectable, HR >140/min, altered mental status). Rapid sequence intubation is planned. Which drug is the agent of choice for induction in this patient with severe hemorrhagic shock?

Explanation

## Induction Agent of Choice in Hemorrhagic Shock **Key Point:** Etomidate is the preferred induction agent in hemorrhagic shock because it maintains hemodynamic stability with minimal effects on blood pressure, heart rate, and cardiac output — critical in a patient with severe hypovolemia. ## Pharmacodynamic Profile in Shock | Agent | Cardiac Output | SVR | BP Effect | Airway | Preferred in Shock? | |-------|---|---|---|---|---| | **Etomidate** | ↔ Maintained | ↔ Maintained | ↔ Minimal change | ↔ Preserved | **YES** | | Propofol | ↓↓ Decreased | ↓↓ Decreased | ↓↓ Severe drop | ↓ Suppressed | NO | | Thiopental | ↓ Decreased | ↓ Decreased | ↓ Moderate drop | ↓ Suppressed | NO | | Midazolam | ↓ Decreased | ↓ Decreased | ↓ Moderate drop | ↓ Suppressed | NO | ## Mechanism of Etomidate's Hemodynamic Stability 1. **Preserved sympathetic tone** — does not suppress catecholamine release 2. **Direct myocardial effects minimal** — maintains contractility 3. **Baroreceptor reflexes intact** — allows compensatory tachycardia 4. **Rapid onset and short duration** — ideal for RSI **High-Yield:** Etomidate is the ONLY induction agent that maintains blood pressure in hemorrhagic shock. All other agents cause vasodilation and/or myocardial depression. ## Caveat: Adrenal Suppression **Warning:** A single dose of etomidate causes transient suppression of 11β-hydroxylase, reducing cortisol synthesis for 24–48 hours. However, in the acute resuscitation phase of hemorrhagic shock, this is NOT a contraindication — hemodynamic stability takes priority. Steroid supplementation is not routinely recommended for single-dose etomidate in trauma. **Clinical Pearl:** In a patient with Class IV shock (undetectable BP, altered mental status), losing blood pressure during induction with propofol or thiopental can precipitate cardiac arrest. Etomidate's preservation of hemodynamics is life-saving. ## Why Alternatives Are Wrong - **Propofol:** Causes profound vasodilation and myocardial depression; can cause cardiovascular collapse in hypovolemic patients - **Thiopental:** Myocardial depressant; increases risk of hypotension and arrhythmias in shock - **Midazolam:** Slower onset than etomidate; not ideal for RSI; still causes hemodynamic depression [cite:ATLS 10th Edition; Stoelting's Pharmacology in Anesthesia Ch 6]