Bupivacaine decreases epidural meperidine requirements after abdominal surgery

The purpose of this study was to determine the optimal of three concentrations of bupivacaine (0.0%, 0.05%, 0.10%) to add to an epidural infusion of meperidine (1 mg.ml-1) for postoperative pain relief.

In this prospective, double blind study, 60 patients undergoing abdominal surgery with general anaesthesia were randomized into three groups to receive for postoperative epidural analgesia: 1) 1 mg.ml-1 meperidine (0% group), 2) bupivacaine 0.05% and 1 mg.ml-1 meperidine (0.05% group), 3) bupivacaine 0.10% and 1 mg.ml-1 meperidine (0.10% group). Postoperatively, the epidural infusion rate was titrated to produce adequate analgesia and pain was assessed at rest and on movement.

There were no differences in demographic data, average pain scores or side effects among the three groups. However, there was improvement of pain relief at rest over time in the three groups (P < 0.05). Postoperative epidural analgesic infusion rates increased over time for the three groups (P < 0.05) and were lower in the 0.10% group (mean of 10.0 ml.hr-1) than in the 0% group (mean of 12.6 ml.hr-1) (P < 0.05). More than half of the 0% group had serum meperidine concentrations > 400 g.L-1 to control moderate postoperative pain.

Although analgesia was identical among groups, the lower serum concentrations of meperidine support the addition of bupivacaine 0.10% to meperidine when administered as a continuous infusion following abdominal surgery.