Study of the possible interaction between fentanyl and propofol using a computer-controlled infusion of propofol

A computer-controlled infusion of propofol designed to achieve a target blood concentration of propofol 3 microgram ml-1 was used to investigate the possibility of an interaction between propofol and fentanyl in 32 patients undergoing body surface surgery. In 16 patients who were not receiving a neuromuscular blocker during maintenance anaesthesia with 67% nitrous oxide, there were no significant differences in blood concentrations of propofol between eight patients who received fentanyl 5 micrograms kg-1 before induction of anaesthesia, and eight patients who did not. In a further 16 patients who received vecuronium during maintenance anaesthesia with 67% nitrous oxide, there were no significant differences in blood propofol concentrations between eight patients who received fentanyl 5 micrograms kg-1 before induction of anaesthesia, and eight patients who did not. Fentanyl administered i.v. immediately before a computer-controlled infusion of propofol resulted in more satisfactory anaesthetic conditions than when fentanyl was not used, but did not significantly prolong the recovery time.