Development of a peripheral nerve stimulator-guided technique for equine pudendal nerve blockade.

This research article focuses on the development of a new method for equine pudendal nerve block using a peripheral nerve locator. The study shows that this procedure is a feasible, safe, and reliable alternative for both epidural and general anesthesia in horses undergoing particular reproductive surgeries.

Methodology and Experimentation

• The researchers carried out their study in two experiments. The first experiment focused on determining the relationship between muscle contractions in the anal and perineal regions and the nerves serving these areas. For this, six ponies were used, and methylene blue dye was injected using an electrolocation technique to map the nerve stimulations.
• The result of the first experiment demonstrated that an effective approach to the pudendal nerve was possible when both anal and perineal twitch were induced during the electrolocation process.
• In the second experiment, the researchers worked on finding the appropriate volume of anesthetic solution for nerve blockage. To do this, they used seven Thoroughbred horses. After the horses were euthanized, a lidocaine/methylene blue solution mixture was injected post-positive electrolocation.
• A segment of 2 cm or longer of the nerve marked by the dye was considered successfully anaesthetized. It was determined that both 10 and 20 mL per injection site resulted in effective nerve staining, indicating successful blockage.

Real-world Application

• Finally, the newly developed method was tested on 27 horses that were admitted for selected reproductive surgical procedures like perineoplasty, urethroplasty, clitorectomy in mares, and penile examination, phallectomy, and urethrostomy in geldings.
• The surgical time varied from a few minutes to 3 hours. The anesthetic used (lidocaine, mepivacaine, or bupivacaine) was selected based on the required duration of analgesia.
• In the end, the researchers concluded that the peripheral nerve stimulator-guided pudendal nerve block technique is a feasible, safe, and reliable alternative to general or epidural anesthesia. The volume of anesthetic solution used was 20 mL and 10 mL per injection site in mares and males, respectively.