An improved lidocaine infusion protocol for cardiac surgical patients

A new protocol for lidocaine administration was tested to determine whether it would provide higher free and total serum lidocaine concentrations during and after weaning from cardiopulmonary bypass (CPB), without leading to accumulation toxicity, than those resulting from a conventional protocol (1.5 mg/kg loading dose bolus + 2 mg/min infusion rate). Ten elective adult cardiac surgical patients were studied. Ten seconds prior to aortic cross-clamp release (0 min), each patient received a lidocaine bolus (1.5 mg/kg) and simultaneous lidocaine infusion (5 mg/min for 1 hour, followed by 2 mg/min for 23 hours). Weaning occurred 20 to 30 minutes after cross-clamp release. Lidocaine levels were determined from arterial blood samples at 0, 10, 20, 30, and 60 minutes, and at 2, 4, and 24 hours postcross-clamp release. Compared with the conventional protocol, the new protocol showed a significant increase in mean total lidocaine concentration (P less than or equal to 0.02) at 30 and 60 minutes, and a significant increase in mean free lidocaine concentration (P less than or equal to 0.005) at 20, 30, and 60 minutes. No patient had toxic levels at 24 hours. Results of this study suggest that in patients undergoing cardiac surgery, a "5 + 2" mg/min infusion protocol is safe and superior to a conventional protocol in achieving therapeutic serum levels of free and total lidocaine.