Development of a peripheral nerve stimulator-guided technique for equine pudendal nerve blockade.
Authors: Gallacher K, Santos L C, Campoy L, Bezuidenhout A J, Gilbert R O
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Peripheral Nerve Stimulator-Guided Pudendal Nerve Blockade in Horses Pudendal nerve blocks offer a targeted analgesic approach for equine perineal and reproductive surgery, yet reliable localisation techniques have been lacking in clinical practice. Gallacher and colleagues developed and validated a peripheral nerve stimulator-guided blockade technique through three sequential experiments: first mapping the anatomical relationship between elicited muscle contractions (anal and/or perineal twitches) and target nerves using methylene blue dye in six ponies; second determining effective anaesthetic volumes (10–20 mL) in seven post-euthanasia Thoroughbreds via dissection; and finally performing the block in 27 clinical cases undergoing procedures including perineoplasty, clitorectomy, phallectomy and urethrostomy. The protocol proved reliably effective across surgical cases of varying duration (minutes to 3 hours), with anaesthetic choice (lidocaine, mepivacaine or bupivacaine) tailored to procedure length and volume adjusted by sex (20 mL in mares, 10 mL in males). This technique provides equine practitioners with a practical, safe alternative to epidural or general anaesthesia for perineal surgery, offering superior regional analgesia with reduced systemic effects—particularly valuable for older or systemically compromised patients where general anaesthesia carries greater risk.
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Practical Takeaways
- •Practitioners can use a peripheral nerve stimulator to reliably perform pudendal nerve blocks for reproductive surgery, requiring elicitation of both anal and perineal twitches to confirm correct needle placement
- •Use 20 mL per injection site in mares and 10 mL in males; choice of local anesthetic (lidocaine, mepivacaine, or bupivacaine) depends on required duration of analgesia
- •This technique provides an effective alternative to general anesthesia for routine reproductive procedures, potentially reducing anesthetic risk and recovery time in clinical patients
Key Findings
- •Pudendal nerve block was successfully achieved when both anal and perineal muscle contractions were elicited during electrolocation
- •Both 10 mL and 20 mL volumes of lidocaine/methylene blue solution produced effective nerve staining of 2 cm or more
- •Peripheral nerve stimulator-guided pudendal nerve blockade provided reliable peri-operative analgesia in 27 horses undergoing reproductive surgery with surgical times up to 3 hours
- •The technique proved feasible and safe as an alternative to epidural anesthesia and general anesthesia for reproductive procedures