Lidocaine Pharmacokinetics in Children during General Anesthesia

In spite of the increasing use of intravenous lidocaine in the operating room, no pharmacokinetic data exist for intravenous lidocaine in children. We studied ten children, ages 0.5-3 yr, and eight adults to determine lidocaine pharmacokinetics during anesthesia with halothane, nitrous oxide, and oxygen. After induction of anesthesia, tracheal intubation, and insertion of venous and arterial catheters, lidocaine, 1 mg/kg, was infused intravenously over 30 sec. Arterial samples were drawn at 0.5, 1, 2, 4, 5, 10, 15, 30, 60, 90, and 120 min. Plasma was separated and analyzed for lidocaine, using gas chromatography. Plasma concentration vs time data were fitted to a two-compartment model. Using standard formulas, we derived the following data: Children: distribution half-life (t 1/2 alpha) 3.2 min, elimination half-life (t 1/2 beta) 58 min, volume of the central compartment (V1) 0.22 L/kg, volume of distribution (Vd area) 1.1 L/kg, and total plasma clearance (Cl) 11.1 ml X kg-1 X min-1. Adults: t 1/2 alpha 3.6 min, t 1/2 beta 43 min, V1 0.16 L/kg, Vd area 0.71 L/kg, and Cl 9.8 ml X kg-1 X min-1. No significant differences were found between children and adults for all parameters analyzed. We conclude that children older than 6 months of age distribute and eliminate intravenous lidocaine in the same manner as adults.