Relative effects of xylazine-atropine, xylazine-atropineketamine, and xylazine-atropine-pentobarbital combinations and time-course effects of the latter two combinations on brain stem auditory-evoked potentials in dogs

SUMMARY Brain stem auditory-evoked potentials ( baep ) were recorded in 4 dogs to analyze the relationship between acoustic stimulus intensities and peak latencies of each wave, and to investigate the relative effects of xylazineatropine, xylazine-atropine-ketamine, and xylazine-atropine-pentobarbital combinations and the time-course effects of the latter 2 drug combinations on baep . Click stimulations fixed at a stimulus rate of 10/s and a frequency of 4 kHz were delivered at intensities ranging from 10- to 110-dB sound pressure level ( spl ) in 10-dB steps for analyzing the relationship between the acoustic stimulus intensities and the peak latencies and at an intensity of 110-dB spl . for investigating the effects of the sedative and anesthetic drug combinations and their timecourse effects on baep . Waves I to VI were identified with stimulus intensity of ≥ 50-dB spl . Wave VII was observed in some records, but was excluded from statistical analysis. As stimulus intensity was increased from 50- to 110-dB spl , the latency decreased for all waves during xylazine-atropineketamine anesthesia. There were no statistically significant differences in the peak latencies of each wave in baep among xylazine-atropine, xylazine-atropine-ketamine, and xylazine-atropine-pentobarbital combinations 20 minutes after drug administration, except that the latency of wave VI during xylazine-atropine sedation was significantly ( P < 0,01) shorter than that detected during xylazine-atropine-ketamine or xylazine-atropine-pentobarbital anesthesia. There were no significant changes in peak latencies of waves I, II, III, V, and VI for 90 minutes after administration of the xylazine-atropine-ketamine combination and for 120 minutes after administration of the xylazine-atropine-pentobarbital combination. It was concluded that baep did not change over time after xylazine-atropine-ketamine or xylazine-atropine pentobarbital administration.