Induction of localized cochlear hypothermia.
CONCLUSIONS
Localized cochlear hypothermia was induced in a rat model, demonstrating the feasibility of modulating cochlear temperature without affecting core body temperature.


OBJECTIVE
Systemic hypothermia has been demonstrated to protect the rat cochlea against electrode insertion trauma-induced hearing loss. Due to potential adverse effects of systemic hypothermia, we set out to demonstrate the feasibility of inducing localized cochlear hypothermia and compared the efficacy of three cooling techniques.


METHODS
Twenty-four ears were prepared by sealing a temperature micro-probe into the basal turn of the cochlea. Cochleae were then cooled by cold saline irrigation of the external auditory canal (EAC) or bulla or by direct application of ice over the bulla. Cochlear temperature measurements were recorded every 30 s during the cooling period until stable. Rectal temperature was monitored continuously and maintained at 36 degrees C.


RESULTS
All techniques resulted in cochlear hypothermia without a concomitant change in rectal temperature. EAC irrigation (14 degrees C and 11 degrees C) decreased cochlear temperature on average by 1.1 degrees C and 1.6 degrees C, respectively. Bulla irrigation (14 degrees C and 11 degrees C) decreased cochlear temperature on average by 3.3 degrees C and 4.1 degrees C, respectively. The ice produced an average cochlear temperature decrease of 4.1 degrees C. In all cases, a cochlear temperature nadir was reached in 5-6 min with no significant differences between groups with respect to time.
Smith
Lee P
LP
Department of Otolaryngology, Leonard M. Miller School of Medicine, University of Miami, Miami, FL 33136, USA.
Eshraghi
Adrien A
AA
Whitley
Douglas E
DE
van de Water
Thomas R
TR
Balkany
Thomas J
TJ
D000818:Animals; D001833:Body Temperature Regulation / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D003051:Cochlea / Q000502:physiology*; D019929:Cochlear Implantation / Q000379:methods*; D007036:Hypothermia, Induced / Q000379:methods*; D009474:Neurons / Q000502:physiology; D051381:Rats; D011916:Rats, Inbred F344