The influence of adrenaline on postoperative analgesia after subarachnoid morphine

A randomised, double-blind study was conducted to investigate the postoperative effects of subarachnoid morphine, with or without adrenaline, after major gynaecological surgery. Seventy-five women having spinal anaesthesia combined with either sedation or general anaesthesia were randomised to receive subarachnoid morphine 0.25 mg with (group MA) or without (group M) adrenaline 200 micrograms; or normal saline (group C). Groups M (n = 22) and MA (n = 25) differed significantly from control (n = 23) with respect to the quality and duration of postoperative analgesia (P < 0.0002) and to a higher incidence of pruritus (P < 0.02). Groups were similar with respect to the incidence of other postoperative side-effects and respiratory data, although the latter showed a trend to less hypoxaemia in the control group. There was no significant difference in any outcome between groups MA and M. It was concluded that, under the study conditions in a post-gynaecological surgery population, the addition of adrenaline to subarachnoid morphine was of no benefit.