Midazolam improves postoperative epidural analgesia with continuous infusion of local anaesthetics

Purpose: Midazolam has been shown to have an analgesic effect by single shot epidural administration. In this study, the effect of midazolam on continuous epidural infusion of bupivacaine was investigated to find a better combination for postoperative analgesia. Methods: Sixty patients scheduled for gastrectomy were divided into three groups of 20. The following mixtures, in 40 ml, were infused continuously over 12 hr after surgery; 40 ml bupivacaine 0.5% in Group C, bupivacaine 0.5% 38 ml + 10 mg midazolam in Group M10, and bupivacaine 0.5% 36 ml + 20 mg midazolam in Group M20. If necessary, 50 mg indomethacin suppository was administered. Blood pressure, heart rate, respiratory rate, analgesia score, and sedation score were monitored for 12 hr after surgery. Amnesia and frequency of the administration of indomethacin suppository were also noted. Results: Blood pressure, heart rate and respiratory rate showed no differences among the groups. Greater sedation was seen in Groups M10 and M20 compared with Group C during first 120 min (P < 0.05). The number of patients with memory was larger in Group C (18) than in Group M10 (10, P = 0.006) and Group M20 (6, P < 0.001). Better analgesia was obtained in patients receiving midazolam than in Group C (P < 0.05). The frequency of the indomethacin administration was 2.0 ± 1.1 (SD) in Group C, which was larger than in Group M10 (1.1 ± 0.9, P = 0.035) and Group M20 (1.2 ± 0.7, P = 0.039). Conclusion: Adding midazolam to a continuous epidural infusion of bupivacaine provides better analgesia, amnesia and sedation than bupivacaine alone without side effects in patients undergoing laparotomy.