The effect of low-dose bupivacaine on postoperative epidural fentanyl analgesia and thrombelastography

We performed a prospective, randomized, double-blind study to determine the effect of bupivacaine on postoperative epidural fentanyl analgesia and thrombelastography in 120 patients who underwent extensive gastrointestinal or genitourinary surgery. The patients were randomized into four groups, 30 patients per group: Group I = epidural fentanyl (EF), 10 μg/mL in saline; Group II = EF with 0.1% bupivacaine; Group III = EF with 0.15% bupivacaine; and Group IV = EF with 0.2% bupivacaine. Pain relief was evaluated by a visual analog scale (VAS), both at rest and during coughing, and by a visual rating scale (VRS). The VAS, VRS, degree of sedation, and side effects (nausea, vomiting, and pruritus) were evaluated every 2 h from 8:00 AM to 6:00 PM, for 24 h after surgery. Forced vital capacities (FVCs) were determined before surgery and at 24 h after surgery. Blood was withdrawn for thrombelastography (TEG) measurements preoperatively, in the recovery room (PARR), and 24 h postoperatively. The VAS, VRS, sedation scores, changes in postoperative FVCs, and the incidence of side effects were not statistically different among the four groups. The 24-h total volumes of infusion in the four groups (146 ± 40 mL, 140 ± 38 mL, 142 ± 40 mL, 124 ± 21 mL, respectively) were not statistically different from each other. There were no significant differences in the TEG values [reaction time (R), coagulation time (K), angle (α), and maximum amplitude (mA)] among the four groups at anytime nor was there any difference between the baseline, PARR, and 24-h TEG values within any group. We conclude that the addition of low-dose bupivacaine does not improve the analgesic effect of an EF infusion or the postoperative coagulation status in this group of patients.