Lignocaine kinetics during cardiopulmonary bypass. Optimum dosage and the effects of haemodilution.

Lignocaine was administered to patients undergoing cardiopulmonary bypass at 28-29 degrees C in bolus doses of 1.5, 2.5 and 3.5 mg kg-1. Plasma concentrations greater than 1.5 micrograms ml-1 were found briefly and inconsistently in patients receiving the usually recommended dose (1.5 mg kg-1), but reliably for 14 min in those receiving 2.5 mg kg-1. The 3.5 mg kg-1 dose produced statistically and clinically significant decreases in mean arterial pressure. Examination of calculated kinetic parameters showed a two-fold decrease in T1/2 alpha, two-fold increases in T1/2 beta and Vss and unaltered ClP and VP when compared with those of unanaesthetized, normothermic patients. The alteration in pharmacokinetics may be attributed largely to decreased binding to albumin following haemodilution.