Bupivacaine pharmacokinetics during epidural anaesthesia in children.

Blood concentrations and pharmacokinetic parameters of bupivacaine were measured after epidural injection in children aged from 1 to 7 years. The children were allocated to two groups. In Group 1 (five children), pharmacokinetic parameters were measured after a single bolus injection of bupivacaine 0.25% with adrenaline 1:200,000. In Group 2 (eight children), pharmacokinetic parameters were measured after the initial injection and the second injection. The same local anaesthetic was used. The volume of the second injection was half of the initial volume. In children of Group 1, maximum mean concentration (CPmax) was 0.64 +/- 0.05 microgram ml-1, time to maximum concentration (Tmax) 19.2 +/- 3.9 min, vascular absorption (T1/2 abs) 4.3 +/- 1.5 min, terminal half-life (T1/2 beta) 227 +/- 37.7 min, volume of distribution (Vd) 3.4 +/- 0.51 kg-1, and total body clearance (Clt) 11.0 +/- 2.0 ml min-1 kg-1. When compared to an adult's pharmacokinetic parameters, both Vd and Clt were increased, so that T1/2 beta remained essentially unchanged. In children of Group 2, the first repeat injection was performed at 110 +/- 6.9 min. Mean CPmax increased significantly (20% after the second injection), whereas the values of the pharmacokinetic parameters measured did not differ significantly from those measured in children in Group 1. The results obtained in the present study demonstrate that the pharmacokinetic parameters of bupivacaine in children do not differ markedly from those reported in adults and that in the recommended dosage, the mean maximum concentrations, even after the second injection, are less than the presumed toxic levels.