Hypoxaemia and pain relief after lower abdominal surgery: comparison of extradural and patient-controlled analgesia.

We have examined postoperative pain in patients allocated randomly to receive extradural bolus diamorphine 3.6 mg, extradural infusion of 0.15% bupivacaine with 0.01% diamorphine or patient-controlled i.v. administration of diamorphine at a maximum rate of 1 mg per 5 min, after total abdominal hysterectomy. Extradural infusion analgesia produced the smallest pain scores from 12 to 24 h after surgery (P < 0.05). More patients in the extradural infusion group were moderately hypoxaemic (SpO2 < 90% > 12 min h-1) after operation, compared with the two other groups (P < 0.05). The group using patient-controlled analgesia received more diamorphine and suffered a greater incidence of emetic sequelae (P < 0.05).