Depression of the guinea pig cochlear temperature caused by anesthesia and ventral‐approach ear surgery

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Abstract
A chronic implant of a thermocouple on the round window membrane of the guinea pig cochlea determined the cochlear temperature in awake, anesthetized (dial in urethane, Rompun, ketamine, Xylocane) and surgically dissected animals. The normal cochlear temperature was equal to the core (rectal) temperature of the guinea pig (38.5.degree. C) and exactly tracked changes in core temperature in the intact animal, at least down to the 33.degree. C level tested here. Ventral surgery to expose the cochlea results in a decrease to a low value of 31.degree. C in cochlear temperature because of the removal of tissue mass overlying the auditory bulla. Effective use of a heating pad and blanket cover over the body of the guinea pig will regulate core temperature, but the exposed cochlea will always have a lower value than either the temperature measured rectally or in the orophraynx.