Effects of Different Target-controlled Concentrations of Remifentanil on MAC_(BAR) of Sevoflurane

Objective: To determine the effects of different target-controlled concentrations of remifentanil on the sevoflurane requirement for blunting sympathetic responses after surgical incision (MACBAR). Methods: 72 patients scheduled for elective abdominal surgery were randomly allocated to four groups. Group R0 received sevoflurane alone, group R1, R2 and R3 received sevoflurane plus remifentanil (target-controlled plasma concentration of 1, 2 and 3 ng·mL -1, respectively). MACBAR determination was made using the reformative up and down method. Results: The MACBAR of sevoflurane were (3.04 ± 0.20)%, (1.52 ± 0.24)%, (0.76 ± 0.13)% and (0.32 ± 0.16)% respectively in the group R0, R1, R2 and R3. The difference in the four groups was very significant (P 0.01). Targetcontrolled concentration of 1, 2 and 3 ng·mL -1 remifentanil reduced the MACBAR of sevoflurane by 50%, 75% and 89%. Conclusion: Target-controlled infusion of remifentanil decreased MACBAR of sevoflurane evidently. MACBAR of sevoflurane decreased gradually with target-controlled concentrations increasing of remifentanil.