Comparison of lidocaine, xylazine, and xylazine/lidocaine for caudal epidural analgesia in horses.

This research study evaluates the efficacy and safety of using different drugs (namely lidocaine, xylazine, and a lidocaine/xylazine combination) for caudal epidural analgesia in horses.

Research Methodology

• The study was conducted on six adult horses, and each horse was tested a total of three times, once a week.
• The three different methods of analgesia tested included lidocaine, xylazine, and a combination of lidocaine and xylazine, injected through an epidural catheter placed in the horse’s tail region.
• The effectiveness of each analgesic drug was assessed by its ability to numb the horse’s perineal area (the region around the anus and genitals) to a pinprick or pressure from a hemostat.

Research Findings

• The results showed that there was no significant difference in the onset time of analgesia between lidocaine and the lidocaine/xylazine combination. This was around 4.3 minutes for lidocaine and 5.3 minutes for the combination.
• The onset of analgesia with xylazine alone was significantly longer, taking approximately 32 minutes to take effect.
• When it came to the duration of the analgesia, the lidocaine and xylazine combination stayed effective for significantly longer (about 330 minutes) than either of the drugs used alone. Lidocaine provided numbing effects for around 87 minutes, and xylazine for approximately 204 minutes.
• None of the administered drugs significantly affected the horses’ pulse and respiratory rates, indicating that they were likely safe to use in this context. Additionally, there were no observable neurological side effects from the use of the drugs or from the epidural catheterization technique used.

Interpretation and Conclusions

• This research suggests that a combination of lidocaine and xylazine can provide quick, long-lasting, and safe analgesia for horses undergoing caudal epidural analgesia.
• While the use of lidocaine alone also provides quick analgesia, its effects do not last as long as the drug combination. Xylazine alone took significantly longer to initiate analgesia but maintained the effects for a longer period compared to lidocaine alone.
• The fact that none of the drugs significantly affected the horses’ vital signs or had observable neurological side effects underscores the safety of the analgesic methods tested.