Intratesticular mepivacaine versus lidocaine in anaesthetised horses undergoing Henderson castration.
Authors: Crandall Alycia, Hopster Klaus, Grove Annie, Levine David
Journal: Equine veterinary journal
Summary
# Intratesticular Mepivacaine versus Lidocaine in Equine Castration When performing Henderson drill castrations under general anaesthesia, achieving adequate cremaster muscle relaxation is essential for surgical efficiency and animal welfare, yet the relative efficacy of common local anaesthetics had not been directly compared in this context. Crandall and colleagues randomised 34 anaesthetised stallions to receive 10 mL of either lidocaine or mepivacaine injected directly into each testicle, with a five-minute interval before incision, whilst both surgeon and anaesthetist remained blinded to treatment allocation. Mepivacaine demonstrated significantly superior cremaster relaxation, with mean scores of 1 on a three-point scale compared to 2 for lidocaine (P = 0.03–0.04 across both testicles), and the lidocaine group required supplementary ketamine boluses in 25% of cases versus only 16% in the mepivacaine group; surgical time, recovery quality and other perioperative parameters showed no meaningful differences. For practitioners performing routine castrations with limited time for local anaesthetic diffusion, intratesticular mepivacaine may offer a practical advantage in reducing cremaster reflex and the associated need for additional sedation, though the authors acknowledge that single-injection methodology and absence of post-operative pain assessment constrain the generalisability of these findings.
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Practical Takeaways
- •Use intratesticular mepivacaine instead of lidocaine for Henderson castration under general anesthesia to achieve superior cremaster relaxation and reduce need for supplemental anesthesia
- •The 5-minute interval between local anesthetic injection and surgical incision is a practical timeframe that allows adequate local anesthetic effect
- •Better cremaster relaxation with mepivacaine translates to potentially easier surgical manipulation and improved anesthetic stability during the procedure
Key Findings
- •Mepivacaine produced significantly better cremaster muscle relaxation (average score 1) compared to lidocaine (average score 2) on both testicles (P=0.03 first testicle; P=0.04 second testicle)
- •Lidocaine group required additional ketamine boluses in 25% of horses versus 16% in the mepivacaine group
- •No significant differences observed in heart rate, respiratory rate, surgical time, or recovery quality between groups
- •Intratesticular injection followed by 5-minute wait before incision was the protocol used