title: Auditory brain stem response testing in anesthetized horses.
abstract: Auditory brain stem response testing, using insert earphones, was performed in 10 healthy horses given general anesthesia. The procedure involved clicks of alternating polarity delivered at a rate of 25 clicks/s. Wave forms, including five peaks, were commonly identified. Latencies were measured in milliseconds for waves I through V for all intensities. Latencies of all waves decreased as stimulus intensity increased. For waves I through V, a least-squares regression line was determined for each horse, using all responses between 87-dB sound pressure level (SPL) and 136-dB SPL, inclusive. Slopes were significantly (P less than 0.05) less than zero for waves I through IV, but not for wave V. Peak latencies of each wave averaged at 87-dB SPL for waves I through V were 1.73, 2.6, 3.82, 4.80, and 5.71 ms, respectively; latencies of these five waves at 136-dB SPL were 1.36, 2.2, 3.06, 3.92, and 4.71 ms, respectively. The decrease in latency among the five waves ranged from 0.13 to 0.004 ms/dB. When peak values were below 87-dB SPL, waves became essentially unrecognizable.
mesh_terms: D000768:Anesthesia, General / Q000662:veterinary; D000818:Animals; D001300:Audiometry, Evoked Response / Q000662:veterinary*; D005072:Evoked Potentials, Auditory; D005260:Female; D006736:Horses / Q000502:physiology*; D008297:Male; D012044:Regression Analysis; D000159:Vestibulocochlear Nerve / Q000502:physiology*