Immediate and prolonged effects of pre- versus postoperative epidural analgesia with bupivacaine and morphine on pain at rest and during mobilisation after total knee arthroplasty.

Thirty-two patients scheduled for total knee arthroplasty were randomized to receive an identical epidural blockade initiated 30 min before surgical incision (N = 16), or at closure of the surgical wound (N = 16). Before induction of general anaesthesia the epidural catheter was tested with bupivacaine 7.5 mg.ml-1, 2 ml. General anaesthesia was induced with thiopentone, pancuronium or atracurium, and fentanyl 0.1-0.3 mg, and maintained with N2O/O2 and enflurane. The epidural regimen consisted of a bolus of 16 ml of bupivacaine 7.5 mg.ml-1 plus morphine 2 mg, and continuous infusion of bupivacaine 1.25 mg.ml-1 plus morphine 0.05 mg.ml-1, 4 ml.h-1 for the first 24 h, and bupivacaine 0.625 mg.ml-1 plus morphine 0.05 mg.ml-1, 4 ml.h-1, for the next 24 h after operation. Additional morphine 2.5-5 mg was administered i.v. or i.m. for the first 24 h postoperatively, and ketobemidone or morphine 5-10 mg orally or rectally from 24 h to 7 d postoperatively, on request. Paracetamol 1000 mg every 8 h was administered from 48 h to 7 days postoperatively. No significant differences were observed in request for additional opioids, or in pain scores at rest or during mobilisation of the operated limb, during or after cessation of the epidural regimen. These results do not suggest timing of analgesia with a conventional, continuous epidural regimen to be of major clinical importance in patients undergoing total knee arthroplasty.