THE EFFECTS OF ANESTHESIA ON OTOACOUSTIC EMISSIONS

We have measured transient-evoked and distortion-product otoacoustic e missions (OAEs) in the chinchilla and compared them in the awake and a nesthetized animal (using either ketamine or barbiturate agents). We r eport a significant increase in OAE amplitudes during anesthesia, part icularly using ketamine. These effects are most evident for transient- evoked otoacoustic emissions (TEOAEs) as measured in the non-linear mo de. Our data support the hypothesis that tonic activity levels in coch lear efferents may be reduced by anesthetic effects, either directly o r indirectly (e.g., by general reductions in descending pathway activi ty), and that reduced cochlear efferent activity will result in the ob served increase of OAE amplitudes.