Sedation and antisedation as tools in equine lameness examination

A kinematic study was performed to establish the locomotion pattern of horses under detomidine sedation and the effects of antagonization for possible use during lameness examinations in uncooperative horses. The kinematics of 17 Warmblood horses (9 sound, 8 lame with chronic forelimb lameness) were recorded on 2 days using a high-speed video system while trotting (3.9 m/s) on a treadmill. On each day a control measurement was carried out prior to sedation with detomidine (10 micrograms/kg bwt) and repeated recordings at 15, 25, 35, 45 and 60 min after sedation. On the second day, sedation was antagonized using atipamezole (100 micrograms/kg bwt) after the 15 min recording. Head height and pulse rate documented the level of sedation. The head dropped from mean 1.23 m (s.d. 0.13) to 0.50 m (0.26) following sedation to reach again 1.06 m (0.19) after 60 min. Antagonization reversed the height significantly at the 25 min recording to 1.06 m (0.11). Walking and trotting were possible in all sedated horses in response to voice commands only. Forelimb lameness symmetry parameter (Head Acceleration Asymmetry: HAAS) in 8 lame horses did not change significantly due to sedation. Stride length increased significantly from mean 2.53 m (0.18) to 2.66 m (0.20) 15 min after sedation and reversed to 2.56 (0.17) m after antagonization. Stride and stance durations changed accordingly. In conclusion, sedation did not change the degree of lameness, but did alter the general locomotion pattern. Antagonization diminished most of these effects, but small differences to the unsedated pattern remained.