[Epidural midazolam with bupivacaine--optimal dose for postoperative pain relief]

Optimal dose of epidural midazolam with bupivacaine for postoperative pain relief was investigated. Forty seven patients for upper abdominal surgery were divided into 5 groups. Each group had either 0.25% bupivacaine 6 ml (control group), 0.25% bupivacaine 6 ml + midazolam 0.025 mg.kg-1 (0.025 group), 0.05 mg.kg-1 (0.05 group), 0.075 mg.kg-1 (0.075 group), or 0.1 mg.kg-1 (0.1 group) administered epidurally for complaint of first postoperative pain. Blood pressure (BP), heart rate (HR), respiratory rate (RR) and sedation score (SS) were monitored for 120 minutes, and the time interval for next analgesics (TNA) was checked. In each group, BP fell down 10 minutes after injection, HR was unchanged, and RR (except for 0.1 group) decreased, compared with the preinjection level. There was no difference between control group and others in BP, HR and RR. But 3 cases in 0.075 group and 4 cases in 0.1 group needed chin lift with a pillow under the shoulder for slight airway obstruction. The most optimal SS was obtained in 0.05 group. TNA was significantly longer in 0.025 and 0.05 groups than in the control group. It was concluded that the optimal dose of epidural midazolam with 0.25% bupivacaine 6 ml was 0.05 mg.kg-1 for postoperative pain relief after an upper abdominal surgery.