Influence of atipamezole on effects of midsacral subarachnoidally administered detomidine in mares.

The research investigates the impact of using atipamezole on mares who have been administered detomidine, examining effects on pain relief, cardiovascular and respiratory function, and limb positioning. The study indicates atipamezole can reverse most effects of detomidine, apart from decreases in heart and breath rate.

Study Design

• The study was conducted using a sample of 10 healthy mares, with a randomized, blinded, and crossover study design.
• Each subject was given detomidine, dissolved in 3 ml of Cerebrospinal fluid (CSF), through midsacral subarachnoidally, followed by either atipamezole or sterile saline solution 61 minutes later as a test or control condition.
• These were administered intravenously. The mares then received a saline solution, again through midsacral subarachnoidally, two weeks later.

Determination of Analgesia and Monitoring

• Analgesia was determined through the inability to perceive sensory stimulation at the perineal dermatome and non-responsiveness to needle-prick stimulation, ranging from the coccygeal to T15 dermatomes.
• Several physiological measures, such as arterial acid-base content, gas tensions, PCV, total solids concentration, heart and respiratory rates, and rectal temperature and arterial blood pressure, were measured.
• The mares were also observed for sweating and urination.

Results of Subarachnoidally Administered Detomidine

• The administration of detomidine resulted in pain relief in the perineal area, significant head drooping, changes in limb position, cardiovascular and respiratory depression, sweating in areas experiencing analgesia, and increased urination.
• The average onset of perineal analgesia was around 9 minutes, lasting approximately 130 minutes.

Effects of Atipamezole on Detomidine

• On the other hand, atipamezole effectively reduced the scores of detomidine-induced pain relief, head drooping, changes in limb position, sweating, and diuresis.
• Atipamezole was also found to partially counteract the decrease in heart rate caused by detomidine, but it did not affect the detomidine-induced decrease in breath rate.

Conclusion

• The study concluded that most of the effects of detomidine, except for slowing of heart and breath rates, could be reversed using atipamezole.
• This suggests that most of the impacts of detomidine are likely through the activation of alpha2-adrenergic receptors on the cell surface.