A 32-year-old woman with a 6-month history of GERD presents to the emergency department with acute appendicitis. She is scheduled for emergency appendicectomy under general anesthesia. On examination, she is anxious, blood pressure 128/82 mmHg, heart rate 98/min, respiratory rate 18/min. She has not fasted for 8 hours. The anesthesiologist plans rapid sequence induction. Which of the following is the MOST appropriate choice for induction agent in this high-risk aspiration scenario?

Explanation

## Induction Agent Selection in RSI with Aspiration Risk ### Clinical Context This patient has multiple aspiration risk factors: - Unfasted (6-hour NPO violation) - GERD history - Emergency surgery - Hemodynamically stable (BP 128/82, HR 98) ### Why Etomidate Is Optimal **Key Point:** Etomidate is the induction agent of choice in RSI when aspiration risk is high AND hemodynamic stability is critical. **High-Yield:** Etomidate's advantages in RSI: 1. **Minimal airway reflexes suppression** — maintains protective airway tone longer than propofol 2. **Cardiovascular stability** — maintains BP and HR (critical in emergency patients who may be hypovolemic) 3. **Rapid onset** — allows quick intubation within the RSI window 4. **No histamine release** — unlike atracurium/mivacurium ### Comparative Analysis of Induction Agents in RSI | Agent | Aspiration Risk | CV Stability | Airway Reflexes | RSI Suitability | |-------|-----------------|--------------|-----------------|----------------| | **Etomidate** | ✓ Best | ✓ Excellent | ✓ Preserved | ✓ **FIRST CHOICE** | | Propofol | ✗ Poor | ✗ Hypotension | ✗ Suppressed | ✗ Avoid in RSI | | Thiopental | ✗ Poor | ✗ Hypotension | ✗ Suppressed | ✗ Avoid in RSI | | Midazolam | ✗ Poor | Variable | ✗ Suppressed | ✗ Avoid in RSI | ### Mechanism: Why Etomidate Preserves Airway Protection Etomidate acts on GABA~A~ receptors with **minimal depression of brainstem airway reflexes** compared to other induction agents. This allows: - Cough reflex preservation during laryngoscopy - Faster glottic closure if aspiration occurs - Reduced risk of silent aspiration **Clinical Pearl:** In RSI, the goal is rapid intubation with cuffed tube placement *before* protective reflexes are completely lost. Etomidate's selective CNS depression achieves this balance. ### Dosing in RSI - **Etomidate:** 0.2–0.3 mg/kg IV (rapid onset in 15–30 seconds) - Followed immediately by succinylcholine 1–1.5 mg/kg (depolarizing) or rocuronium 1.2 mg/kg (non-depolarizing) **Warning:** Single-dose etomidate does NOT cause clinically significant adrenal suppression in RSI context — the "adrenal crisis" concern applies only to infusions or repeated dosing in ICU. ### Why Other Agents Fail in This Scenario **Propofol:** Causes profound myocardial depression, peripheral vasodilation, and airway reflex loss — unacceptable in emergency surgery where hypovolemia is possible. **Thiopental:** Obsolete in modern RSI; causes severe hypotension and airway reflex suppression. **Midazolam:** Slower onset (60–90 seconds), unreliable in RSI, causes airway reflex loss without the speed of etomidate. [cite:Morgan & Mikhail's Clinical Anesthesiology 6e Ch 13]