POSTOPERATIVE ANALGESIA WITH EPIDURAL BUPIVACAINE AND LOW-DOSE FENTANYL - A COMPARISON OF 2 CONCENTRATIONS

Background: The purpose of the study was to compare the analgesic and side effects of two epidurally administered mixtures of bupivacaine an d fentanyl with the same drug ratios. Methods: One hundred patients sc heduled for colorectal surgery were randomized to receive a thoracic e pidural infusion of either bupivacaine 0.12% with fentanyl 2 mu g/ml o r bupivacaine 0.24% with fentanyl 4 mu g/ml during 48 h postoperativel y. The pumps were adjusted to keep the visual analogue scale (VAS) pai n score at 3 or less (on a scale of 0-10) with a minimum of adverse ef fects. Results: There were no statistically significantly differences between the two groups in VAS pain scores. The average VAS pain score resting varied between 0.5 and 1, and coughing between 1.9 and 3.4. On e case of respiratory depression with breathing frequency 7 occurred i n each group, but none of the patients required naloxone. One patient in the low concentration group developed partial motor weakness in bot h legs 36 h postoperatively. Equal drug amounts - bupivacaine 10.8-11 mg/h and fentanyl 18-18.4 mu g/h - were given in both groups throughou t the study. Conclusions: Both groups had low pain scores with few and comparable adverse effects. It thus seems that the volume is not impo rtant when mixtures of bupivacaine and fentanyl in the studied concent rations are infused epidurally at a low thoracic level. Practical reas ons favour the higher concentration mixture.