The influence of diamorphine on spinal anaesthesia induced with isobaric 0.5% bupivacaine.

In a randomised, double-blind study, the effect of addition of 1 mg of diamorphine to 4 ml of 0.5% bupivacaine for spinal anaesthesia was studied in two groups each of 30 patients presenting for either transurethral genito-urinary surgery, or for lower limb arterial surgery or inguinal herniorrhaphy. Addition of 1 mg diamorphine to intrathecal 0.5% bupivacaine produced a prolonged and satisfactory analgesia in more than half the patients undergoing lower limb arterial or inguinal surgery, and the analgesic requirements of the remainder during the first postoperative 24 h were much less than those who received bupivacaine alone. In the urological surgery set there were no significant differences between the group who received bupivacaine and diamorphine, and the group who received bupivacaine alone. The mixture of diamorphine 1 mg in 4 ml 0.5% bupivacaine was slightly less hypobaric (0.9981 at 37 degrees C) than bupivacaine alone.