ED50 of remifentanil for providing excellent intubating conditions when co-administered with a single standard dose of propofol without the use of muscle relaxants in children: dose-finding clinical trial.

Purpose: Previous studies evidenced that orotracheal intubation without neuromuscular blockers is feasible in children and has some potential advantages. Remifentanil has favorable pharmacodynamic and pharmacokinetic properties as an opioid for orotracheal intubation, but its dose for excellent intubation conditions when co-administered with propofol has not been established. This study was designed to find the minimum effective dose of remifentanil for excellent intubation conditions of children when co-administered with propofol, without neuromuscular relaxant drugs.

Method: Blinded adaptive clinical trial, with sequential allocation of 27 children between 2 and 9 years-old, American Society of Anesthesiologists' physical status PI or PII, scheduled for elective surgery under general anesthesia. Remifentanil dose began at 2 µg/kg and varied by 0.25 µg/kg according to the sequential allocation up-and-down rule designed by Dixon and Massey. Remifentanil was infused in 30 s and followed by propofol (3 mg/kg) in 20 s. Laryngoscopy and intubation were performed and assessed using Viby-Mogensen criteria, 90 s after the end of opioid administration. Inclusion of patients stopped after six crossovers, and remifentanil effective dose was estimated using pooled adjacent-violators algorithm.

Results: Remifentanil effective dose for 50% was established in 3.04 µg/kg (IC 95% 2.68-3.11, p < 0.05). The most frequent adverse effect was difficult positive pressure facial mask ventilation, which occurred in four children (15%).

Conclusion: Minimum remifentanil effective dose for providing excellent intubating conditions when co-administered with a single standard dose of propofol without the use of neuromuscular blockers in children is 3.04 µg/kg.

Trial Registration: NCT02454868.