Effect of the infusion rate of propofol on the onset time of rocuronium.

Background: Administration of propofol, especially rapid administration, decreases patient cardiac output (CO) to various degrees. CO might influence the buildup of an effective drug level within the neuromuscular junction and affect the onset time of neuromuscular blockers. The present study aimed to investigate the effects of different infusion rates of propofol on patient CO and the onset time of rocuronium.

Methods: A total of 90 patients were randomly assigned to receive propofol (2.5 mg/kg) at an infusion rate of 480 mg/min (group A), 240 mg/min (group B), or 120 mg/min (group C). After the administration of propofol, rocuronium (0.6 mg/kg) was administered to facilitate tracheal intubation. The Finometer monitor was used to obtain the cardiovascular profile during the induction of general anesthesia. Neuromuscular relaxation was monitored by acceleromyography using the ulnar nerve at the wrist surface and electrodes with repeated single twitches. Onset time was defined as the time from the beginning of rocuronium injection until 95% twitch depression. The onset time of rocuronium in the three groups was compared using analysis of variance with the post-hoc Tukey test. A p-value <0.05 was considered statistically significant.

Results: After induction, a significant decrease in CO was observed in group A (21.6% ± 4.6%) when compared with the findings in group B (11.6% ± 4.5%) and group C (9.8% ± 4.6%). The onset time of rocuronium was significantly longer in group A (177.7 ± 17.6 seconds) than in group B (121.3 ± 18.3 seconds) and group C (118.3 ± 12.3 seconds).

Conclusion: Rapid administration of propofol significantly delays the onset time of rocuronium by altering CO as measured with the Finometer monitor.