Sedation and antisedation as tools in equine lameness examination.

The study investigated the influence of detomidine sedation and its reversal on the trotting locomotion of both healthy and chronically lame horses, with the results suggesting that while the sedation alters the general locomotion patterns, it doesn’t significantly affect the degree of lameness.

Research Methodology

• The researchers carried out their experiments on 17 Warmblood horses, of which 9 were sound and 8 showed signs of chronic forelimb lameness.
• The movement, or kinematics, of these horses was documented over two days using a high-speed video system as the horses trotted at a speed of 3.9 m/s on a treadmill. This allowed the researchers to capture any changes in locomotion.
• For each day, the horses’ movement patterns were first recorded without any intervention. Following this, the horses were sedated using a drug named detomidine before being filmed again at intervals of 15, 25, 35, 45, and 60 minutes post-sedation.
• On the second day of the experiment, another medication called atipamezole was administered to the horses 15 minutes after sedation to reverse its effects. The impact of antagonizing the sedation was studied by making recordings after the 15 min mark.

Key Findings

• The sedation caused the height of the horses’ heads to decrease significantly, indicating a state of relaxation. This lower head height was observed to gradually rise again over time, which signifies a reduction in the effect of sedation. After the antagonization, there was a significant increase in head height in just 10 minutes.
• It was found that walking and trotting were possible in all sedated horses following voice commands only.
• The researchers measured a parameter called Head Acceleration Asymmetry (HAAS) in the 8 horses with lameness. Despite the sedation, the symmetry in this parameter didn’t change considerably, which means the degree of lameness remained mostly unaffected by sedation.
• An increase in stride length was noticed after sedation, and stride length then returned close to its initial measurement after the antagonization.

Conclusion

• The research concluded that while sedation altered locomotion patterns in horses, it didn’t significantly change the degree of their lameness.
• The use of the antagonist drug mostly reversed the effects of sedation, although small deviations from the unsedated locomotion pattern were observed.
• This study has potential implications for the use of detomidine sedation during lameness examinations, especially in horses that are uncooperative during the procedure.