EPIDURAL DIAMORPHINE INFUSIONS WITH AND WITHOUT 0.167-PERCENT BUPIVACAINE FOR POSTOPERATIVE ANALGESIA

Forty patients who underwent upper or mid-abdominal surgery were rando mly allocated to receive a post-operative epidural infusion of 0.083 m g ml-1 of diamorphine in either 0.167% bupivacaine or 0.9% NaCl soluti on. The nursing staff, who were unaware of which solution was being in fused, managed the patients' pain according to a standardized scheme. They adjusted the epidural infusion rates to 3, 5 or 7 ml h-1 accordin g to the patient's hourly reports of pain on a four point verbal ratin g scale (none, mild, moderate or severe), aiming to use the lowest all owed infusion rate to prevent or reduce any pain that was more than mi ld. Additional analgesia was given as diclofenac 75 mg intramuscularly if the patients report moderate pain while on the highest infusion ra te. The nurses were instructed to summon anaesthetic help if pain reli ef was still unsatisfactory after diclofenac, but this was never neces sary. Diclofenac was needed by six patients receiving diamorphine in s aline and one receiving diamorphine in bupivacaine (P<0.05). The range of average hourly epidural infusion rates was constrained by design t o between 3 and 7 ml h-1 but the median of these values was 5 ml h-1 i n the diamorphine-saline group and 3.35 ml h-1 in the diamorphine-bupi vacaine group (P<0.02). In patients receiving diamorphine in saline, a median of 6 (range 0-16) of the 24 h reports were of more than mild p ain, whereas in the diamorphine-bupivacaine group, the corresponding f igures were 2 (range 0-13) (P<0.02)). There were 12 (median) exacerbat ions of pain by coughing (range 2-24) in the diamorphine-only group an d 8 (range 0-12) in the diamorphine-bupivacaine group (P<0.02).