Development and Clinical Application of Pudendal Nerve Block Using A Peripheral Nerve Locator for Reproductive Surgery in Horses

Abstract

AimsTo develop, describe and evaluate clinical applicability of pudendal nerve block using a peripheral nerve locator.MethodsIn a pilot study, 6 ponies were used to determine the correlation between nerves serving the perineal region (namely pudendal, caudorectal and perineal nerves) and the muscle contractions observed when an electrolocation technique was used. After appropriate electrolocation a small volume of lidocaine/methylene blue solution was injected under general anaesthesia. The dye location relative to the specified nerves was examined after humane euthanasia followed by dissection of the relevant region. In a second experiment, 7 Thoroughbred horses were used to evaluate the appropriate volume of lidocaine solution for the nerve block. Lidocaine/methylene blue solution was injected after positive electrolocation immediately (5–40 min) after euthanasia. A stained segment of 2 cm or more of the nerve was deemed to be sufficient and was evaluated after dissection. Finally, evaluation of a bilateral pudendal nerve block was used to provide anaesthesia and analgesia in 10 clinical cases involving both mares and geldings.ResultsAnal twitch alone was associated with injection of the caudal rectal nerve, whereas combined twitch of the anus and perineum was required for reliable location and injection of the pudendal nerve. Injection was more accurate in standing rather than laterally recumbent horses. A volume of 10–20 ml bilaterally, reliably provided at least 60 min of clinical analgesia for perineal surgery. Procedures satisfactorily completed included; urethral extension and perineal body repair in mares and penile examination, removal of penile tumours and penile amputation in male patients.Conclusions and practical significancePudendal nerve block is a practical and effective alternative to epidural analgesia for selected standing surgical procedures of the reproductive tract in male and female horses.Ethical animal researchThe Cornell University Institutional Animal Care and Use Committee approved the project and informed client consent was obtained. Sources of funding: None. Competing interests: None.