PLASMA-CONCENTRATIONS OF BUPIVACAINE IN NEONATES AFTER CONTINUOUS EPIDURAL INFUSION

This study reports plasma bupivacaine concentrations in 13 neonates wh o received lumbar epidural anesthesia during major abdominal surgery. A bolus of 1.8 mg/kg of bupivacaine (2.5 mg/mL) was administered after induction of anesthesia, followed by a continuous infusion of 0.2 mg . kg(-1). h(-1) (1.25 mg/mL). Plasma concentrations of total and free bupivacaine and alpha 1-acid-glycoprotein (AAG) were determined. Resul ts are presented as mean (+/- SEM). At 48 h, five of nine patients sti ll had increasing total plasma concentrations, and the total bupivacai ne concentrations ranged between 0.7 and 3.1 mu g/mL. The plasma level s of AAG increased significantly between 1 and 24 h (4.3 +/- 2.3 nM an d 7.7 +/- 2.3 nM, respectively) (P = 0.018). The free concentrations o f bupivacaine were relatively unchanged at 1 and 24 h (84 +/- 20 ng/mL and 58 +/- 15 ng/mL, respectively). No adverse events occurred during the study period. In conclusion, the dose administered in this study appears to be safe. However, a substantial number of patients still ha d increasing concentrations of total plasma bupivacaine at 48 h. Furth ermore, the interindividual variation was considerable. These observat ions cause concern about the safety of epidural infusions longer than 48 h in the age group studied.