INFLUENCE OF ANESTHESIA ON AUDITORY EVOKED RESPONSE

Abstract

Auditory brainstem response (ABR) and auditory middle latency response (MLR) in 128 patients were recorded during the surgical operation which was performed under the various anesthetic methods and conditions. The relation between the anesthetic methods and the charac- teristics of the auditory evoked responses was investigated. From the results, the anesthesia could be classified into following three types : type A such as enflurane-nitrous oxide-oxygen and halothane-nitrous oxide-oxygen anesthesia by which both ABR and MLR were affected, type B such as thiamylal and diazepam anesthesia by which only MLR was affected, and type C such as neuroleptanesthesia (NLA), high dose fentanyl, ketamine, althesin, spinal and epidural anesthesia, by which both ABR and MLR were not affected. Therefore, when ABR and MLR are recorded as a monitor of the eighth nerve surgery, NLA would be the most adequate and available method.
On the other hand, it was proved that ABR and MLR were markedly affected by the decrease of body temperature. Therefore, the decrease of body temperature should be taken into considera- tion when the auditory evoked response of comatous patients was monitored.