Changes In Hearingacuity Foilowing Different Forms Of Anaesthetic Techniques:

Akram Mohamed El Gindy

-61-SummaryThe aim of this work is to study effect of differentanaesthestic techniques on the aUditory acuity.The study was conducted in 120 patients who were provedto be clinically free otologic disease. The patient hadperformed non otological surgery. They divided into four equalgroups :Group ICosisted of 30 patients who were anaesthestized bynitrous oxide. Their age ranged between 12 and 50 years.Group IIConsisted of of patients who were anaesthestized byspinal intradural anaesthesia. Their age ranged between 14 and51 years.Group IIConsisted of 30 patients who were anaesthestized byspinal epidural anaesthesia. Their age ranged between 11 and47 years.Group IVConsisted of 30 patients who were anaesthestized byEther. Their age ranged between 13 and 50 years.-62-In all four groups. audiogram was performed before theoperation. after the operation by 24 hours and after theoperation by 72 hours.After nitrous oxide anaesthesia by 24 hours. theaudiogram showed significant -P<0.05- hearing loss for all.But after the operation by 72 hours the hearing was improvedand the loss became non significant. This phenomenon can .beexplained by the fact that N20 diffuses rapidly into themiddle ear causing increasing in its pressure which willcauses some hearing loss.The audiogram which taken after 24 hours for the caseswho were anaesthestized by spinal intradural anaesthesia.showed a significant -P 0.05- shown the aUdiogram. Thishearing loss affects mainly the low frequencies. This resultcan be explained by the fact that spinal puncture andinjection cause changes in the pressure of the C.S.F. Thesechange will be transmitted via the cochlear aqueduct to the-63-cochlear perilyph causing distotion of the basilar membrane~mainly at the apex of the cochlea. this is the thinest andbroadest part of the membrane and responsible for perceptionof low frequencey acoustic stimuli. anaesthesia by ether hadno effect on auditory acuity as proved by the aUdiometry.