Plasma concentrations of bupivacaine in neonates after continuous epidural infusion.

This study reports plasma bupivacaine concentrations in 13 neonates who 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. Results are presented as mean (+/-SEM). At 48 h, five of nine patients still had increasing total plasma concentrations, and the total bupivacaine concentrations ranged between 0.7 and 3.1 micrograms/mL. The plasma levels of AAG increased significantly between 1 and 24 h (4.3 +/- 2.3 nM and 7.7 +/- 2.3 nM, respectively) (P = 0.018). The free concentrations of 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 had increasing concentrations of total plasma bupivacaine at 48 h. Furthermore, the interindividual variation was considerable. These observations cause concern about the safety of epidural infusions longer than 48 h in the age group studied.