الفهرس 
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Abstract
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Summary
The aim of this work is to study effect of different
anaesthestic techniques on the aUditory acuity.
The study was conducted in 120 patients who were proved
to be clinically free otologic disease. The patient had
performed non otological surgery. They divided into four equal
groups :
Group I
Cosisted of 30 patients who were anaesthestized by
nitrous oxide. Their age ranged between 12 and 50 years.
Group II
Consisted of of patients who were anaesthestized by
spinal intradural anaesthesia. Their age ranged between 14 and
51 years.
Group II
Consisted of 30 patients who were anaesthestized by
spinal epidural anaesthesia. Their age ranged between 11 and
47 years.
Group IV
Consisted of 30 patients who were anaesthestized by
Ether. Their age ranged between 13 and 50 years.
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In all four groups. audiogram was performed before the
operation. after the operation by 24 hours and after the
operation by 72 hours.
After nitrous oxide anaesthesia by 24 hours. the
audiogram showed significant -P<0.05- hearing loss for all.
But after the operation by 72 hours the hearing was improved
and the loss became non significant. This phenomenon can .be
explained by the fact that N20 diffuses rapidly into the
middle ear causing increasing in its pressure which will
causes some hearing loss.
The audiogram which taken after 24 hours for the cases
who were anaesthestized by spinal intradural anaesthesia.
showed a significant -P<O.05 hearing loss in 76 % of the
cases. After 72 cases. the audiogram showed improvement of the
hearing of these cases.
Significant hearing loss -P< 0.05- was also shown by
aUdiogram taken 24 hours a~ter the spinal epidural
anaesthesia. in 73 % of the cases. The’hearing loss in those
22 cases improved 72 hours after the operation and the loss
became non significant -p> 0.05- shown the aUdiogram. This
hearing loss affects mainly the low frequencies. This result
can be explained by the fact that spinal puncture and
injection cause changes in the pressure of the C.S.F. These
change will be transmitted via the cochlear aqueduct to the
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cochlear perilyph causing distotion of the basilar membrane
~
mainly at the apex of the cochlea. this is the thinest and
broadest part of the membrane and responsible for perception
of low frequencey acoustic stimuli. anaesthesia by ether had
no effect on auditory acuity as proved by the aUdiometry.