Effect of Xylazine, Detomidine, and Detomidine–Butorphanol Combination on Latencies of Peaks I–V of Brainstem Auditory–Evoked Responses in Horses

• Reports on the effect of sedative drugs on BAERs are contradictory.
• BAERs obtained without sedation and with three sedative protocols were compared.
• Wave III latency and IPL I-III were significantly increased with detomidine.
• Detomidine increases conduction time in the auditory pathway.
• Detomidine possibly increases conduction time by inhibiting the locus coeruleus.

Literature reports on the effect of sedative and anesthetic drugs on the first five peaks of brainstem auditory–evoked responses (BAERs) are somehow contradictory. In particular, no data are available on the effect of sedatives on BAER in horses. The objective of the study was to evaluate the influence of sedation with xylazine, detomidine, and detomidine–butorphanol combination on latencies of BAER peaks in horses. The absolute peak latencies of waves I, II, III, and V and interpeak latencies (IPLs) I–III, III–V, and I–V obtained in nine Bardigiano horses without sedation and with each of the sedation protocols were statistically compared. A statistically significant (P < .05) increase of the latency of wave III and of the IPL I–III was present in horses sedated with detomidine compared with the subjects not sedated or sedated with xylazine. An effect of detomidine on conduction time along the auditory pathway is suspected. These results must be taken into account when using α2-agonists with greater affinity for specific receptors, such as detomidine, for sedation of animals undergoing BAER for clinical or research purposes.