Effects of sodium pentobarbital, ketamine, halothane, and chloralose on brainstem auditory evoked responses.

A parametric study was performed in cats comparing the effects on the brainstem auditory evoked response of four anesthetic agents used either in the operating room or the laboratory: sodium pentobarbital, ketamine, halothane, and chloralose. Each anesthetic agent was administered to each of four cats in varying sequence. Click-evoked brainstem auditory evoked responses (BAER) were compared for differences in wave form configuration, latencies, and amplitudes of the component peaks. Five distinct peaks (I to V) could be identified in the brainstem auditory evoked responses of every animal using each anesthetic agent. There were no statistically significant differences in mean latencies of the component peaks among anesthetic agents. Amplitude differences of the component peaks between animals using the same anesthetic agent were too large to be meaningfully compared. This study suggests that the click-evoked brainstem auditory response is a useful means of monitoring the integrity of the ascending auditory pathway during neurosurgical procedures as the wave form and latencies of the component peaks are not affected by a variety of parenteral and inhalation anesthetic agents.