Abstract: Objective To evaluate the sedative effect of epidural anesthesia and interaction between epidural anesthesia and propofol using bispectral index (BIS). Methods 40 patients undergoing elective abdominal operation with general anesthesia participated in the study. After placing the epidural catheter, the patients were randomly allocated to 2 groups receiving either 5 mL of 1% lidocaine through the epidural catheter (group L) or 5 mL of epidural normal saline (group S), with 20 patients in each group. 8 minutes later, after confirmation of epidural administration, group L received 5～10 mL of combination of 1% lidocaine and 0.5% ropivacaine, whereas group S received 8 mL of epidural normal saline. BIS, MAP, HR and SpO2 were recorded before epidural injection, 8 min after first epidural injection, 15 min after first epidural injection and 30 min after first epidural injection. 30 min after first epidural injection, general anesthesia was induced with propofol via target-controlled infusion pump, the initial plasma concentration was 4 μg/mL. The effect site concentration of propofol when BIS firstly achieved 50 was recorded by another anesthesiologist who is blinded to the grouping. Following that, remifentanil and rocuronium were administrated to accomplish the endotracheal intubation. Follow-up was made for each patient postoperatively to identify possible intraoperative awareness. Results There were no significant changes in BIS after epidural infusion in both groups, and no significant differences exist between groups at all time points regarding BIS. The effect site concentration of propofol on BIS 50 in group L was significantly less than group S (P = 0.0157), 2.1 ± 0.5 μg/mL vs. 2.5 ± 0.5 μg/mL, respectively. Conclusion Epidural anesthesia alone doesn’t exert sedative effect measured by BIS. However, when combined with propofol, epidural anesthesia can potentiate the sedative effect of propofol.

Key words: Monitoring, bispectral index, Anesthesia, epidural, Propofol