## Drug of Choice for RSI in Haemodynamic Instability **Key Point:** Etomidate is the induction agent of choice in haemodynamically unstable trauma patients undergoing emergency intubation because it maintains cardiovascular stability better than other induction agents. ### Mechanism of Haemodynamic Preservation Etomidate causes minimal reduction in systemic vascular resistance and maintains baroreceptor reflexes, making it ideal when: - Blood pressure is critically low (< 90 mmHg systolic) - Ongoing fluid resuscitation is incomplete - Rapid sequence intubation is needed for emergency airway control ### Comparison of Induction Agents in Trauma | Agent | Cardiovascular Effect | Airway Reflexes | Use in Shock | | --- | --- | --- | --- | | **Etomidate** | Minimal ↓ BP, maintains SVR | Preserved | **Preferred** | | Propofol | Marked ↓ BP, ↓ SVR | Preserved | Contraindicated | | Thiopental | Marked ↓ BP, ↓ HR | Preserved | Contraindicated | | Midazolam | Variable, slower onset | Preserved | Not ideal for RSI | **Clinical Pearl:** In this case, the patient remains hypotensive despite 2 units of O-negative blood, indicating ongoing hypovolemia and shock. Propofol and thiopental would cause further cardiovascular collapse. **High-Yield:** Etomidate is the standard induction agent for RSI in: - Haemorrhagic shock - Septic shock - Cardiogenic shock - Any critically hypotensive patient requiring emergency airway control **Warning:** Do not use propofol in hypotensive trauma patients — it causes profound vasodilation and myocardial depression, potentially fatal in shock states. **Tip:** Remember the ATLS principle: in unstable trauma requiring intubation, choose the agent that preserves perfusion pressure — that is etomidate.
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