BACKGROUND: The induction and maintenance of intravenous anesthesia by propofol-TCI has been popular. When infusing propofol with other drugs at the same intravenous access line, incompatibility may result. We attempted to evaluate the incompatibilities between propofol and rocuronium by subtherapeutic dosing of rocuronium.

METHODS: Eighty patients were randomized into two groups. Induction of anesthesia was done by propofol-TCI. The patients in group 1 received rocuronium 0.6 mg/kg at the same intravenous access line with propofol infusion and in group 2 received rocuronium at the different intravenous access line with propofol infusion. One Hz single twitch responses were measured by acceleromyography after rocuronium administration. Intubation was done when the twitch height depressed more than 95% of the baseline. The intubating conditions were assessed and graded as excellent, good, poor and bad. Onset time, recovery index and duration were compared between the two groups.

RESULTS: The onset was significantly delayed in group 1 (124.9 ± 35.5 vs. 101.8 ± 22.1), but there were no significant differences in the intubating condition, recovery index, duration and the incidence of withdrawal response to rocuronium injection.

CONCLUSIONS: Onset time was delayed when administrating rocuronium at the same intravenous access line with propofol-TCI. So giving rocuronium at the different intravenous access line with propofol infusion would be helpful to achieve adequate intubating condition rapidly.