COMPARISON OF EXTRADURAL FENTANYL, BUPIVACAINE AND 2 FENTANYL-BUPIVACAINE MIXTURES FOR PAIN RELIEF AFTER ABDOMINAL-SURGERY

Fentanyl 50 mu g, bupivacaine 50 mg and two mixtures containing fentan yl 50 mu g and bupivacaine 25 mg or 12.5 mg (0.25 and 0.125 %), respec tively, in a volume of 10 ml were administered via thoracic extradural catheters to 24 patients after major abdominal surgery. All patients received all four treatments, in a randomized order, so that each pati ent received one of the 24 possible combinations of the four treatment s. Pain relief was assessed by a linear analogue pain scale and the Pr ince Henry Hospital pain score. The duration of pain relief, effects o n ventilatory frequency, heart rate, arterial pressure and central ven ous pressure were also recorded. Mean reductions in the analogue pain scale for fentanyl, bupivacaine, and fentanyl in 0.25 % and 0.125 % bu pivacaine were 80 (SEM 5) %, 87 (4) %, 86 (5) % and 77 (5) %, respecti vely (ns). Pain scores decreased by 62 (6) %, 83 (5) %, 77 (6) % and 7 2 (6) %, respectively (ns). Mean arterial pressure decreased to 90 (2) %, 70 (2) %, 81 (2) % and 82 (3) %, respectively, of pretreatment val ues. In this respect, bupivacaine alone was significantly different fr om the three other treatments (P < 0.001). Hypotension (reduction in a rteria[ pressure greater than 25 % of pretreatment mean arterial press ure) was also more frequent after bupivacaine alone (P < 0.01). Effect s on ventilation, heart rate and central venous pressure did not diffe r between the four treatments. We conclude that in patients who had un dergone major abdominal surgery, analgesia after thoracic extradural i njection of fentanyl 50 mu g did not differ significantly from analges ia after 0.5 % bupivacaine 10 ml, or the fentanyl-bupivacaine mixtures . Bupivacaine alone caused a greater decrease in arterial pressure and a higher incidence of hypotension than fentanyl or the fentanyl-bupiv acaine mixtures.