Epidural fentanyl markedly improves thoracic epidural analgesia in a low-dose infusion of bupivacaine, adrenaline and fentanyl - A randomized, double-blind crossover study with and without fentanyl

Background: The objectives of the present study were to evaluate the effect s on postoperative pain intensity, pain relief, and side effects when remov ing fentanyl from an optimally titrated epidural infusion consisting of bup ivacaine, fentanyl and adrenaline. Methods: A prospective, randomized, double-blind, crossover study was carri ed out in 20 patients after major upper abdominal surgery requiring a large longitudinal incision. Patients with only mild pain when coughing during t horacic epidural infusion of about 10 ml per hour of bupivacaine 1 mg . ml( -1), fentanyl 2 mug . ml(-1), and adrenaline 2 mug . ml(-1) were included. On the 1st and 2nd postoperative days, each patient was given a double-blin d epidural infusion, at the same rate, with or without fentanyl. The effect s were observed for 6 h or until pain when coughing became unacceptable in spite of rescue analgesia. Rescue analgesia consisted of up to two patient- controlled epidural bolus injections (4 ml) per hour and intravenous morphi ne if necessary. Results: Main outcome measures, i.e. pain intensity when coughing and at re st, increased (P<0.001) when fentanyl (19.2+/-5.2 <mu>g . h(-1)) was omitte d from the epidural infusion: after 6 h pain intensity when coughing had in creased to unacceptable levels in spite of increased consumption of rescue bupivacaine and adrenaline (P<0.001). Within 15-20 min after restarting the triple epidural mixture with fentanyl, pain intensity was again reduced to mild pain when coughing. Conclusions: A low dose of epidural fentanyl (20 <mu>g . h(-1)) markedly im proved the pain-relieving effect of bupivacaine and adrenaline infused epid urally at a thoracic level after major upper abdominal surgery. This dose o f fentanyl is much too small to relieve severe dynamic pain when given syst emically. Therefore, this study indirectly supports the view that a low-dos e thoracic epidural infusion of fentanyl has a spinal analgesic site of act ion.