Extradural diamorphine with adrenaline in labour: comparison with diamorphine and bupivacaine

In a randomized double-blind study of 51 primigravida, we have examined the relative efficacies of bupivacaine, diamorphine or diamorphine with adrenaline given by the extradural route for relief of pain during labour. Group 1 (n = 18) received diamorphine 5 mg in 0.9% sodium chloride 8 ml; group 2 (n = 19) received diamorphine 5 mg in 0.9% sodium chloride 8 ml with 1:200,000 adrenaline; group 3 (n = 14) received 0.375% bupivacaine 8 ml. All patients received 0.375% bupivacaine 8 ml as a supplement after the initial analgesia had subsided. Patients in all groups had satisfactory and comparable analgesia 20 min after the initial injection. However, after 60 min and up to 8 h, analgesia was superior in group 2 as assessed by linear analogue pain scores, with statistical significance at 4, 6 and 8 h. Groups 1 and 2 required bupivacaine supplements less frequently than group 3 (P less than 0.001). There were no serious adverse effects in any group, but pruritus was a feature in the diamorphine groups. Diamorphine 5 mg may be used as an alternative to bupivacaine 0.375% 8 ml in the first stage of labour and provides a longer duration of action. The addition of adrenaline 1:200,000 appears to augment both the quality and duration of analgesia.