Antinociceptive effects of low dose lumbosacral epidural ropivacaine in healthy ponies.

This research study investigates the effectiveness and safety of using a low dose of lumbosacral epidural ropivacaine, a local anesthetic, in ponies. Its main finding is that this method could serve as a reliable pain relief solution for ponies, exerting maximum impact on lumbosacral and sacrococcygeal regions.

Objective of the Research

• The primary goal of this study was to ascertain the safety and effectiveness of applying a mild dose of lumbosacral epidural ropivacaine in ponies. Ropivacaine, being a local anesthetic, was expected to alleviate pain in ponies.

Methodology

• The pain-relieving (antinociceptive) effects of this anesthetic were assessed using mechanical nociceptive thresholds (MNTs) across different spinal levels in conscious ponies. These measurements helped determine any increase in tolerance to mechanical strain.
• The impact of the anesthetic on transmitting pain signals to the spinal cord was gauged by evaluating spinal cord somatosensory evoked potentials (SSEPs) in anesthetized ponies. This was crucial in understanding how the anesthetic impacted the sensory response to nerve stimulations.
• The impairment of motor functions, specifically coordination, was measured via ataxia scores collected from conscious ponies.
• The design of this study was a randomized, placebo-controlled, double-blind crossover.

Main Findings

• The application of mild lumbosacral epidural ropivacaine resulted in a threshold increase for MNTs at several anatomical points, exhibiting a maximum effect at the lumbosacral and sacrococcygeal regions, both with respect to threshold elevation and duration of the impact.
• Investigating the SSEPs indicated that ropivacaine influenced both Aβ- and Aδ-mediated transmission of nociceptive afferent transmission to the spinal cord at the lumbosacral junction.
• While mild ataxia was observed following the application of ropivacaine, all ponies remained standing, suggesting that the motor function was mildly but not critically affected.

Conclusion

• The use of low dose lumbosacral epidural ropivacaine was deemed safe and effective in providing antinociceptive effects in both conscious and anaesthetised ponies. Thus, its inclusion could bring substantial value to multimodal analgesic protocols in Equidae.