Effect of preoperative extradural bupivacaine and morphine on stump sensation in lower limb amputees.

We have examined the effect of preoperative extradural bupivacaine and morphine on postoperative stump sensation in 31 patients undergoing amputation of the lower limb in a prospective, randomized, double-blind study. Patients were allocated randomly to one of two groups: group 1 received extradural 0.25% bupivacaine 4-7 ml h-1 and morphine 0.16-0.28 ml h-1 before and during operation; group 2 received extradural saline before and during amputation and conventional analgesics for pain treatment. All patients received general anaesthesia for the amputation and extradural bupivacaine and morphine after operation. Sensory examination of the limb/stump was carried out before amputation, and after 1 week and 6 months. The following were measured: pressure pain thresholds (pressure algometry), touch and pain detection thresholds (von Frey hairs), thermal sensibility (thermal rolls), and allodynia and wind-up-like pain. There were no differences between the two groups at any of the postoperative assessments for mechanical and thermal sensibility or rate of allodynia and wind-up-like pain. Our study suggests that preoperative and intraoperative extradural block had no long-term prophylactic effect on hyperalgesia, allodynia or wind-up-like pain.