[Clinical manifestations and serum fentanyl concentrations during epidural high dose fentanyl anesthesia]

Twelve elective abdominal surgeries were performed under epidural anesthesia with high dose fentanyl. An epidural catheter was inserted at Th9-Th12 interspace and fentanyl 10 micrograms.kg-1 with [E (+)] or without [E(-)] epinephrine 1:100,000 was given for each group of 6 patients. After the administration of epidural fentanyl, arterial blood was sampled at 5, 10, 15, 30, 60, 120, 180, 240 minutes. The serum concentrations of fentanyl were measured by gas chromatography. The peak concentration of serum fentanyl was observed in the E (-) group, while that was not seen in the E (+) group. The time of reach maximum serum concentration after epidural fentanyl administration in the E (-) group was from 10 to 15 minutes. In two cases of E (-) group, the plasma concentration-time course could be fitted to two-compartment model. The others could be fitted neither to a two-compartment nor to a three-compartment model. In both groups, we could maintain anesthesia with enflurane of less than 0. 4%, and N2O, 66%. It is suggested that analgesic effect of fentanyl on opioid receptor of spinal cord plays a major role in this anesthesia method.