What are the onset and duration of etomidate, succinylcholine, and rocuronium for intubation?

Onset and Duration of Etomidate, Succinylcholine, and Rocuronium for Intubation

For rapid sequence intubation, etomidate provides onset within 5-15 seconds with duration of 5-15 minutes, succinylcholine achieves onset within 60 seconds with duration of 4-6 minutes, and rocuronium at 0.9-1.2 mg/kg provides onset within 60 seconds with duration of 30-60 minutes. 1, 2, 3

Etomidate Pharmacokinetics

Onset and Duration:

• Onset of action occurs within 5-15 seconds after intravenous administration 4
• Duration of anesthesia is 5-15 minutes when using the standard dose of 0.3 mg/kg 1, 4
• Immediate recovery from anesthesia is rapid, typically occurring within 3-5 minutes with average dosing 1

Clinical Characteristics:

• Etomidate has minimal respiratory and cardiovascular effects, making it ideal for hemodynamically unstable patients 4
• The 2023 Society of Critical Care Medicine guidelines note that etomidate has a quick onset and short duration of action, though they found no significant difference in mortality or hypotension compared to other induction agents 5

Succinylcholine Pharmacokinetics

Onset and Duration:

• Onset of action occurs within 60 seconds, making it the fastest-acting neuromuscular blocker 2
• Duration of action is 4-6 minutes, significantly shorter than rocuronium 2, 3
• Standard adult dosing for intubation is 1.0 mg/kg 2

Age-Specific Pediatric Dosing:

• Less than 1 month: 1.8 mg/kg 2, 6
• 1 month to 1 year: 2.0 mg/kg 2, 6
• 1-10 years: 1.2 mg/kg 2, 6
• Greater than 10 years: 1.0 mg/kg 2, 6

Clinical Considerations:

• The French guidelines note that succinylcholine remains the preferred first-choice agent for rapid sequence induction in children due to its rapid onset and short duration 5, 6
• The short duration is particularly advantageous if intubation fails, as spontaneous ventilation returns quickly 2

Rocuronium Pharmacokinetics

Onset and Duration:

• At doses of 0.9-1.2 mg/kg, rocuronium provides onset within 60 seconds, comparable to succinylcholine 7, 2, 3
• Duration of action is 30-60 minutes, significantly longer than succinylcholine 2, 3
• At the standard intubating dose of 0.6 mg/kg, onset occurs within approximately 2 minutes with clinical relaxation lasting 33 minutes (range 14-85 minutes) 3

Dose-Dependent Effects:

• 0.6 mg/kg: Onset in ~2 minutes, duration ~33 minutes 3
• 0.9 mg/kg: Onset in ~60 seconds, duration ~58 minutes 3
• 1.2 mg/kg: Onset in ~60 seconds, duration ~67 minutes 3

Pediatric Considerations:

• Time to maximum block is shortest in infants (28 days to 3 months) and longest in neonates 3
• Duration of clinical relaxation is shortest in children (>2 years to 11 years) and longest in infants 3
• The recommended pediatric dose is 0.6 mg/kg, though 0.45 mg/kg may be used depending on anesthetic technique 3

Comparative Clinical Context

Rapid Sequence Intubation:

• For RSI requiring rapid onset, rocuronium must be dosed at ≥0.9 mg/kg (preferably 1.0-1.2 mg/kg) to achieve comparable intubation conditions to succinylcholine 7, 2
• The main disadvantage of rocuronium is its prolonged duration (30-60 minutes vs 4-6 minutes), which necessitates protocolized post-intubation analgosedation to prevent awareness 2
• A large out-of-hospital RCT found first-pass success rates of 79.4% with succinylcholine (1 mg/kg) versus 74.6% with rocuronium (1.2 mg/kg) 2

Special Population Adjustments:

• In geriatric patients, rocuronium exhibits slightly prolonged clinical duration (46-94 minutes depending on dose) 3
• In patients with hepatic disease, rocuronium duration is approximately 1.5 times longer than in patients with normal hepatic function 3
• Initial rocuronium dosing does not require modification in renal or hepatic failure, as onset time remains unchanged despite prolonged duration 7, 3

Critical Pitfall:

• When rocuronium is used instead of succinylcholine, sugammadex should be rapidly available for reversal if needed, particularly in pediatric patients 2