The effects of halothane-and-oxygen anesthesia, and of halothane-nitrous oxide-and-oxygen anesthesia on tympanograms in the dog.

Electroacoustic tympanograms were recorded from both ears of 20 dogs of either sex, aged 6 mo to 12 yrs, prior to anesthesia, at 10 min after halothane- and-oxygen (HO) anesthesia, and at 5 min after nitrous oxide was added to the HO mixture (HNO). Both HO and HNO anesthesia significantly increased compliance and peak pressure values from pre-anesthetic (own control) values. In addition, HNO anesthesia significantly increased peak pressure values above HO anesthesia levels. HNO compliance values were not significantly different from HO values. These results suggest that tympanograms recorded during either HO or HNO anesthesia in the dog will be altered and that interpretation of the tympanograms should include consideration of the state of consciousness of the animal during recording.