Mild hypothermia protects auditory function during cochlear implant surgery.
OBJECTIVE
Loss of auditory function after cochlear implant (CI) electrode insertion occurs in two stages in the laboratory rat. An immediate loss is followed by a progressive loss over 7 days. Similar stages of acute and progressive neuronal loss occur after trauma in the central nervous system where hypothermia has been shown to have a protective effect. We hypothesize that hypothermia has a similar protective effect against loss of auditory function caused by CI electrode insertion trauma.


METHODS
Thirty rats underwent surgery in one cochlea; the contralateral ear was an unoperated control. In the normothermia group, CI electrode insertion trauma was generated with rectal temperature maintained at 37 degrees C throughout the experiment. In the mild hypothermia group, electrode trauma was generated with rectal temperature lowered to 34 degrees C. In the surgical control group, mock surgery was performed at 37 degrees C. Multiple frequency auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) testing of all ears was performed before surgery, immediately afterward, and on postoperative days 3, 5, and 7.


RESULTS
Both ABR and DPOAE testing demonstrated partial loss of auditory function after electrode insertion trauma. However, the hypothermia group had significantly less functional loss in the immediate stage and no significant loss in the progressive stage.


CONCLUSIONS
Mild hypothermia protects auditory function during CI electrode insertion.
Balkany
Thomas J
TJ
Department of Otolaryngology, University Ear Institute, Leonard M. Miller School of Medicine, University of Miami, Miami, FL 33136, USA.
Eshraghi
Adrien A
AA
Jiao
He
H
Polak
Marek
M
Mou
Caihong
C
Dietrich
Dalton W
DW
Van De Water
Thomas R
TR
D000818:Animals; D001831:Body Temperature; D003054:Cochlear Implants; D004566:Electrodes; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D006309:Hearing / Q000502:physiology*; D007036:Hypothermia, Induced / Q000379:methods*; D017084:Otoacoustic Emissions, Spontaneous; D051381:Rats; D011916:Rats, Inbred F344