The effect of changes in arterial CO2 tension on plasma lidocaine concentration

Abstract

The authors studied the effect of changes in arterial carbon dioxide tension on plasma tidocaine concentrations during a constant lidocaine infusion in eight healthy volunteers. With a PaCO2 of 41.4 ±. 0.9mmHg (mean ± SE), total plasma lidocaine concentrations were 3.97 ± 0.20 μg·ml-1. There was no significant change associated with hypercarbia (PaCO2 = 55.7 ± 1.5mmHg, lidocaine = 3.93 ± 0.18 μg±ml-1)or hypocarbia (PaCO2 = 19.5 ± 1.4mmHg, lidocaine = 4.29 ± 0.25 μg·ml-1), despite the known effects of changes in CO2 tension on hepatic blood flow and lidocaine protein binding. During hypercarbia, plasma lidocaine binding decreases while total plasma lidocaine remains essentially constant; therefore, increased CO2 tensions could cause toxicity if total lidocaine concentrations were in the high therapeutic range (5 μg·ml-1). Four subjects experienced transient symptoms of mild lidocaine toxicity during acute increases in carbon dioxide tension. © 1987 Canadian Anesthesiologists.