Comparison of the brainstem auditory evoked responses during sevoflurane or alfaxalone anaesthesia in adult cats.
Objective: To compare the effects of general anaesthesia using sevoflurane or alfaxalone on the brainstem auditory evoked response (BAER) test in adult healthy cats. Study design: Prospective, clinical, 'blinded', crossover study. Animals: Ten feral adult healthy cats. Methods: Premedication consisted of dexmedetomidine (0.01 mg kg-1) intramuscularly (IM). The first general anaesthesia was induced and maintained with sevoflurane (treatment S) for physical examination, BAER test, complete blood tests, thoracic radiographs and abdominal ultrasound. The second general anaesthesia was induced with alfaxalone (treatment A) IM (2 mg kg-1) and maintained with alfaxalone (10 mg kg-1 hour-1) for the BAER test, followed by neutering surgery. The BAER recordings were compared for differences in latencies, amplitudes and waveform morphology. Data were analysed using Student's t test and Wilcoxon rank test for paired samples for parametric and non-parametric data, respectively. Statistical significance was set at p <0.05. Results: General anaesthesia was uneventful; normal BAER comprising five peaks could be identified in both treatments. Mean±SD latencies were 1.05±0.09, 1.83±0.11, 2.52±0.19, 3.43±0.17 and 4.39±0.15 ms and 1.03±0.04, 1.81±0.73, 2.53 ± 0.15, 3.37 ± 0.13 and 4.33±0.13 ms in treatments S and A, respectively. Median (interquartile range) amplitudes were 2.83 (0.67), 1.27 (0.41), 0.30 (0.40), 1.05 (0.82), 0.61 (0.38) microvolts and 2.84 (1.21), 1.49 (1.18), 0.26 (0.32), 0.91 (0.50) and 0.92 (0.64) microvolts in treatments S and A, respectively. There were no statistically significant differences in mean latencies or median amplitudes between both the anaesthetics. Conclusions and clinical relevance: This study demonstrates that there were no statistically significant differences between both the anaesthetics on the BAER test in adult healthy cats. Moreover, two possible anaesthetic protocols are described for cats undergoing this electrodiagnostic test.