Effects of remifentanil on propofol requirements for loss of consciousness in target-controlled infusion

Abstract

Background: We evaluated the effects of various doses of target-controlled remifentanil on the propofol requirements for the loss of consciousness (LOC) and the consequent hemodynamic changes on the induction of intravenous anesthesia in day-case surgery.

Methods: Eighty infertile female patients scheduled for diagnostic laparoscopy were randomly allocated to 1 of 4 groups (20 in each) to receive a target concentration of 1 ng x mL(-1) (Remi-1 group), 2 ng x mL(-1) (Remi-2 group), 3 ng x mL(-1) (Remi-3 group), or 4 ng x mL(-1) remifentanil (Remi-4 group). After equilibrium of remifentanil, propofol was administered with initial target concentration of 2 microg x mL(-1) and with 1 microg x mL(-1) increments. The response to call was assessed every 15 s until a LOC was achieved.

Results: The effect site concentration of propofol (Ce), the total propofol dose, and the time for LOC were significantly decreased with increasing remifentanil concentrations. There was a moderate correlation between the effect of remifentanil and the effect site concentration of propofol at the LOC (r(2) = 0.353, P < 0.05). There was also a moderate correlation between the remifentanil concentration and the time to LOC (r(2) = 0.442, P < 0.05). There were no significant differences in the hemodynamics among the groups, although the decreases in blood pressure after propofol administration in all groups were significant compared with baseline.

Conclusion: The effect of altering the target-controlled remifentanil concentration during propofol induction was found to be dose-dependent. There was no significant difference in the cardiovascular response with the studied range of concentrations of remifentanil and propofol.