[The plasma concentration of buprenorphine during its continuous epidural infusion after catheterization at different vertebral levels].

We investigated 27 patients undergoing elective surgery under epidural anesthesia. The plasma concentration of buprenorphine during its continuous epidural administration was measured by the radioimmunoassay method. We also performed a retrospective study on supplemental analgesics necessary for 48 hours after surgeries. The plasma concentration of buprenorphine was found to be stable at 300 pg.ml-1 during its continuous epidural infusion. The frequencies of administration of supplemental analgesics were 3.3 times with catheterization at upper thoracic vertebral level, 2. 1 times at lower thoracic vertebral level and 1.7 time at upper lumbar vertebral level. We conclude that analgesia with the continuous epidural administration of buprenorphine is satisfactory at low plasma concentration and is superior, considering the necessity of supplemental analgesics to other methods of systemic administration. It is estimated that the epidural distribution volume at lower thoracic and upper lumbar vertebral level is twice the volume at upper thoracic level from plasma buprenorphine concentration.