Auditory brainstem responses during systemic infusion of lidocaine.

Auditory brainstem-evoked responses (ABR) to clicks were recorded in unanesthetized restrained cats before, during, and after systemic intravenous infusion of lidocaine hydrochloride. The drug was infused continuously at varying rates. Lidocaine's major effect on ABR was to lengthen latent periods to all wave-form peaks in proportion with the infusion rate. The effect on latent periods was cumulative throughout the auditory brainstem, ie, all interpeak time intervals increased. Increases in ABR latencies were not due to reductions in effective stimulus intensity because lidocaine did not reduce ABR component amplitudes or increase thresholds. The effects of the drug were reversible. The data are consistent with the notion that lidocaine, directly or indirectly, works throughout the auditory brainstem to increase axonal and synaptic conduction times.