METHODS	The patients in the EPI group ( n = 15 ) had combined epidural analgesia and general anesthesia with sevoflurane and 60 % nitrous oxide in oxygen , followed by the epidural infusion of a 0.125 % bupivacaine and 5 microg x ml ( -1 ) buprenorphine mixture by means of an on-demand analgesic system ( bolus of 2 ml , lockout interval of 60 min , and background infusion of 2 mlxh ( -1 ) ) .\