Research paperComparison between the effects of postanesthetic xylazine and dexmedetomidine on characteristics of recovery from sevoflurane anesthesia in horses

ObjectiveTo compare postanesthetic xylazine and dexmedetomidine on recovery characteristics from sevoflurane anesthesia in horses.Study designRandomized, crossover study.AnimalsSix geldings, mean ± standard deviation (SD) (range), 17 ± 4 (11-24) years and 527 ± 80 (420-660) kg.MethodsHorses were anesthetized with sevoflurane for 60 minutes under standardized conditions for a regional limb perfusion study. In recovery, horses were administered either xylazine (200 μg kg−1) or dexmedetomidine (0.875 μg kg−1) intravenously. Recoveries were unassisted and were video-recorded for later evaluation of recovery events and quality by two individuals unaware of treatment allocation. Recovery quality was assessed using a 100 mm visual analog scale (VAS) (0 = poor recovery, 100 = excellent recovery), the Edinburgh Scoring System (ESS) (0-100; 100 = excellent recovery) and the mean attempt interval (MAI) (longer = better). Data are mean ± SD.ResultsAll recovery quality assessments (xylazine and dexmedetomidine, respectively: VAS: 71 ± 21 mm, 84 ± 13 mm; ESS: 65 ± 22, 67 ± 30; MAI: 52 ± 24 minutes, 60 ± 32 minutes) and events (first limb movement: 37 ± 8 minutes, 42 ± 10 minutes; first attempt to lift head: 44 ± 12 minutes, 48 ± 9 minutes; first attempt to sternal posture: 57 ± 28 minutes, 50 ± 7 minutes; number of head bangs: 2.0 ± 3.0, 0.5 ± 0.5; time to first attempt to stand: 72 ± 6 minutes, 78 ± 13 minutes; time to standing: 79 ± 14 minutes, 84 ± 13 minutes) did not differ significantly between treatments (p > 0.05).Conclusions and clinical relevanceRecovery characteristics did not differ significantly between postanesthetic xylazine and dexmedetomidine following 1 hour of sevoflurane anesthesia in horses in this study. Further evaluations in more horses and in younger horses are required to confirm these results.