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.

Effect of the addition of adrenaline to extradural diamorphine analgesia after caesarean section.

In a randomized double-blind study the effect of the addition of adrenaline to extradural diamorphine was assessed in 54 patients after Caesarean section. Patients received extradural diamorphine 5 mg in saline 10 ml with or without adrenaline 1 in 200,000 for postoperative pain relief. Analgesia was profound and of rapid onset in both groups. Duration of analgesia was greater in the adrenaline group (time to next analgesia 12.51 +/- 0.94 h, mean +/- SEM), than in the saline group (9.87 +/- 0.98 h) (P = 0.057). Analgesia was also more consistent in the adrenaline group, with 77% of patients having more than 8 h of good analgesia compared with 48% in the saline group (P less than 0.05). Plasma morphine concentrations, measured in 12 patients, were lower, although not significantly so, in the adrenaline group and mean time to peak concentration markedly delayed. No serious side effects were observed, but there was a higher incidence of vomiting in the adrenaline group.