EPIDURAL INFUSIONS OF SUFENTANIL WITH AND WITHOUT BUPIVACAINE - COMPARISON WITH DIAMORPHINE BUPIVACAINE

The requirements for supplementary 3 ml epidural injections of bupivac aine 0.5% (top-ups) were used in a randomized double-blind study to co mpare the effects of five types of thoracic epidural infusions given a t 2.5 ml h-1 for the first 24 h after major surgery to the upper abdom en in 99 patients and the lower abdomen in 72. The infusions were: bup ivacaine 0.167% alone; diamorphine 0.167 mg ml-1 (0.417 mg h-1) in bup ivacaine 0.167%; sufentanil 2 mug ml-1 (5 pg h-1) in 0.167% bupivacain e; sufentanil 4 mug ml-1 (10 mug h-1) in 0.167% bupivacaine; and sufen tanil 4 mug ml-1 (10 mug h-1) in normal saline. The patients who had u pper abdominal surgery were on average older than those having lower a bdominal surgery and a larger proportion of them were female. They rec eived on average fewer top-ups. After both upper and lower abdominal s urgery, epidural infusions of bupivacaine alone required the most freq uent supplementation (inter-quartile range 6-14 top-ups in 24 h) and t he two sufentanil-bupivacaine mixtures required the fewest (interquart ile range 0-12 top-ups in 24 h). The infusions of sufentanil without b upivacaine were significantly less effective than the sufentanil-bupiv acaine mixtures after upper (but not lower) abdominal surgery. Althoug h the two sufentanil-bupivacaine mixtures were indistinguishable in an algesic effectiveness after either upper or lower abdominal surgery, t he lower (5 mug h-1) dose rate of sufentanil gave a significantly high er average breathing rate and lower average PaCO2 for the first 24 h a fter lower (but not upper) abdominal surgery. Blood samples were taken (as an afterthought) from 11 patients receiving sufentanil 10 mug h-1 , just before the epidural infusion was stopped. The concentrations we re mostly above the range for systemic analgesia, but below the values that would have been expected if a steady state had been achieved.