Ketamine vs Etomidate for RSI in Trauma Patients
Ketamine offers specific advantages over etomidate in trauma patients requiring RSI, primarily through its sympathomimetic properties that maintain hemodynamic stability, bronchodilation benefits for chest trauma, and avoidance of adrenal suppression, though both agents are considered acceptable first-line choices with no mortality difference. 1, 2
Hemodynamic Advantages of Ketamine
Ketamine preserves blood pressure through endogenous catecholamine release, which is critical in hypovolemic or shocked trauma patients. 1 This sympathomimetic activity maintains cardiovascular stability without the myocardial depression seen with propofol or thiopental. 1 The Society of Critical Care Medicine recommends ketamine as a first-line induction agent alongside etomidate, with particular utility in hemodynamically unstable patients. 1, 2
However, a critical caveat exists: in critically ill patients with depleted catecholamine stores (prolonged shock, severe cardiogenic shock, or adrenal exhaustion), ketamine can paradoxically cause hypotension despite its sympathomimetic properties. 1, 3 Recent meta-analyses confirm this concern, showing ketamine is associated with higher post-intubation vasopressor requirements compared to etomidate (OR 1.30,95% CI: 1.03-1.64). 4, 5
Respiratory Benefits in Trauma
Ketamine causes bronchodilation, which is particularly beneficial in trauma patients with chest injuries, aspiration risk, or underlying reactive airway disease. 1 This contrasts with thiopental, which can cause severe bronchoconstriction. 1
Adrenal Suppression Concerns with Etomidate
Etomidate causes transient adrenal suppression with significantly higher incidence of adrenal insufficiency compared to ketamine (OR 2.43,95% CI: 1.67-3.53). 4 This is particularly concerning in septic patients, where pediatric guidelines explicitly contraindicate etomidate use in septic shock and recommend ketamine instead. 2 However, the 2023 Society of Critical Care Medicine guidelines note that despite etomidate-induced adrenal insufficiency, no evidence demonstrates this causes negative clinical outcomes, and corticosteroid administration following etomidate is not recommended. 6, 2
Mortality and Clinical Outcomes
No significant difference exists in 30-day mortality between ketamine and etomidate in critically ill patients undergoing RSI. 6, 4, 5, 7 The most recent 2025 meta-analysis of 23,926 patients found no mortality difference (RCTs: OR 0.92,95% CI: 0.68-1.24; CCTs: OR 1.16,95% CI: 0.92-1.45). 4 The 2023 Society of Critical Care Medicine guidelines confirm no significant difference between etomidate and other induction agents in mortality, and most studies demonstrated favorable peri-intubation hemodynamics with etomidate. 6
Practical Dosing Algorithm
Administer ketamine at 1-2 mg/kg IV for RSI, using the lower end (1 mg/kg) in patients with cardiovascular compromise to minimize hemodynamic effects while maintaining adequate sedation. 1, 2 Always administer ketamine before the neuromuscular blocking agent to prevent awareness during paralysis. 1, 2
Decision Algorithm for Trauma RSI:
- Hemodynamically stable trauma patients: Either ketamine or etomidate acceptable 6, 2
- Hypovolemic/early shock with intact catecholamine response: Ketamine preferred (1-2 mg/kg) 1
- Prolonged shock/catecholamine depletion: Consider etomidate (0.3 mg/kg) over ketamine due to paradoxical hypotension risk 1, 3
- Chest trauma/bronchospasm risk: Ketamine preferred for bronchodilation 1
- Septic trauma patients: Ketamine strongly preferred over etomidate 2
- Head injury with controlled ventilation: Ketamine safe and appropriate 1, 3
Critical Pitfalls to Avoid
Always have vasopressors immediately available during RSI with any induction agent, as post-intubation hypotension is common and associated with increased mortality. 3 Ketamine increases upper airway secretions, which can be attenuated with atropine or glycopyrrolate pretreatment, particularly important in trauma patients at risk for aspiration. 1
In head-injured patients, historical concerns about ketamine increasing intracranial pressure have been refuted by evidence from 2009-2013, making ketamine safe when used with controlled mechanical ventilation. 1, 3
Comparative Hemodynamic Data
While etomidate traditionally shows favorable hemodynamic profiles, recent registry data reveals nuanced differences. Peri-intubation hypotension rates in emergency department RSI were 18.3% with ketamine versus 12.4% with etomidate. 6, 3 However, a 2021 prehospital study found no difference in the incidence of 20% SBP decrease between agents (16% etomidate vs 18% ketamine). 8
The key distinction is that ketamine's hemodynamic effects depend on endogenous catecholamine availability, making patient selection critical for optimal outcomes. 1, 3