Induction Agent and Dose for Rapid Sequence Intubation
For RSI in critically ill adults, use either etomidate (0.2-0.3 mg/kg) or ketamine (1-2 mg/kg) as your induction agent, as there is no significant difference between them regarding mortality, hypotension, or vasopressor requirements. 1
Primary Recommendation
The 2023 Society of Critical Care Medicine guidelines provide a conditional recommendation (moderate quality evidence) that no difference exists between etomidate and other induction agents for RSI with respect to mortality or peri-intubation hypotension 1. This recommendation is based on a Cochrane meta-analysis of 772 patients showing no mortality difference (OR 1.17; 95% CI, 0.86-1.60) 1.
Agent Selection Algorithm
Etomidate: 0.2-0.3 mg/kg
- Hemodynamically unstable patients: Preferred due to favorable hemodynamic profile
- Dose reduction: Consider 0.15 mg/kg in severely compromised patients 1
- Advantages: Minimal blood pressure effects, rapid onset
- Caution: Single-dose adrenal suppression occurs but does NOT require corticosteroid supplementation 1
Ketamine: 1-2 mg/kg
- Alternative choice: Equivalent outcomes to etomidate 1
- Advantages: Quick onset, preserves respiratory drive, sympathomimetic properties
- Critical caveat: In critically ill patients with depleted catecholamine stores, ketamine can paradoxically cause hypotension and cardiac arrest 1
- Best for: Patients with preserved sympathetic tone
Agents to Avoid in Critical Illness
Propofol: Has the most profound hypotensive effect; limit use in hemodynamically unstable patients 1
Midazolam: Longer onset of action compared to etomidate/ketamine; potent venodilator at RSI doses 1
Essential Best Practice
Always administer a sedative-hypnotic induction agent when using a neuromuscular blocking agent 1. This is a best practice statement to prevent awareness during paralysis, which is a critical patient safety concern.
Evidence Nuances
The guidelines acknowledge conflicting data: one meta-analysis of 29 studies suggested increased mortality with etomidate (RR 1.09; 95% CI, 1.04-1.29) 1, but this was heavily weighted by retrospective studies with significant selection bias. The higher-quality Cochrane review of RCTs showed no mortality difference, which the guideline panel prioritized 1.
A prospective RCT comparing etomidate to ketamine found improved 7-day survival with ketamine but no difference at 28 days, with no explanation for this finding and no differences in vasopressor use, mechanical ventilation duration, or ICU length of stay 1.
Common Pitfalls
- Do not administer corticosteroids after single-dose etomidate for RSI to counteract adrenal suppression (conditional recommendation, low quality evidence) 1
- Avoid using NMBA alone without sedation, even in patients with depressed consciousness—this risks awareness during paralysis 1
- In shock states with catecholamine depletion, ketamine's sympathomimetic properties may fail, leading to cardiovascular collapse 1
Practical Dosing Summary
| Agent | Standard Dose | Reduced Dose (if unstable) |
|---|---|---|
| Etomidate | 0.2-0.3 mg/kg | 0.15 mg/kg |
| Ketamine | 1-2 mg/kg | 1 mg/kg |
| Propofol | 2 mg/kg | Avoid in shock |
| Midazolam | Not recommended for RSI | Not recommended for RSI |
The choice between etomidate and ketamine should be based on individual patient hemodynamics and catecholamine reserve, but both are acceptable first-line agents with equivalent outcomes when used at appropriate doses 1.