Effect of Anesthetic Drugs on Vestibular Evoked Myogenic Potential Recording

The human saccule has preserved the ancestral ability to respond to high-intensity acoustic stimulations, generating a contraction reflex of the cervical tract muscles. Recording the muscular bioelectric potentials following saccular stimulation allows the evidence of the vestibular-evoked myogenic potentials (VEMPs). The aim of this study was to record VEMPs in alert and anesthetized guinea pigs to evaluate the possible different impacts of some anesthetic drugs on VEMP recording. Sixteen guinea pigs, divided into four groups, were employed for the study. Each group underwent general anesthesia induced using different pharmacological regimens; auditory and vestibular functions were examined with Auditory Brain Response (ABR) and VEMP methods. The analysis of the results showed that the VEMPs recording performance was strictly related to the alert status of the guinea pigs: VEMPs were not recordable during anesthesia while reappeared at awakening, with the same temporal and morphological characteristics of pre-anesthesia. ABR was instead normally present during anesthesia without showing any differences with all the various anesthetic drugs employed. These results prompted us to conclude that anesthetic drugs cause the disappearance of saccular reflex in guinea pigs, not minding the specific type of drugs employed. This evidence, in agreement with the data available in literature for humans, induces and encourages future studies about sacculocollic reflex and its possible application in clinical practice.