Bupivacaine 0.125% Improves Continuous Postoperative Epidural Fentanyl Analgesia After Abdominal or Thoracic Surgery

The addition of 0.125% and 0.25% bupivacaine to continuous postoperative epidural infusions of fentanyl, in a 10 micrograms.ml-1 concentration, were studied in 39 patients following abdominal or thoracic surgery in prospective, random, double-blind fashion. Patients received an initial bolus of 0.1 ml.kg-1 of the the study solution and an infusion of 6 ml.hr-1 which was titrated to maintain analgesia (VAS < 40). Assessments of pain (VAS), pulmonary function (pH, PaCO2), and bowel function (time to flatus or po fluids) were made until the second post-operative morning. There was a difference among the three groups in analgesia (means VAS scores) over time (P < 0.01), with the fentanyl-alone group producing less analgesia than the 0.125% bupivacaine group (P < 0.01). There was no difference in the average infusion rates, postoperative pulmonary function, or bowel function. The incidence of side effects including somnolence, nausea and vomiting, and pruritus was also similar. Fewer patients in the 0.125% bupivacaine group than in the 0.25% group developed a transient sensory loss to pinprick and ice (3 vs 10, P < 0.001). Four patients in both bupivacaine groups had leg weakness, those in the 0.125% were all a Bromage 1 score, while in the 0.25% group one had a Bromage 1, one a Bromage 2, and two Bromage 3 scores. The addition of 0.125% bupivacaine improves the analgesia of epidural infusions of fentanyl (10 microgms.ml(-1)) when used following abdominal or thoracic surgery and results in minimal sensorimotor disturbance.