The effect of 0.5 mL mepivacaine administered as an abaxial sesamoid nerve block on lameness of horses with digital pain did not differ significantly from that of 2.5 mL of mepivacaine.

Abstract

OBJECTIVE: To compare the effect of 2.5 mL 2% mepivacaine to the effect of 0.5 mL 2% mepivacaine administered over each palmar digital nerve, as an abaxial sesamoid nerve block (ASNB), to 6 horses lame because of naturally occurring digital pain. METHODS: In a crossover study design with 3 horses in each group, the trotting gait of the horses was analyzed with an inertial sensor-based, motion-analysis system (Q with Lameness Locator; Equinosis LLC) immediately before and after treatment with either 0.5 or 2.5 mL mepivacaine administered over each nerve near the base of the proximal sesamoid bone of the lame forelimb. The gait was reevaluated objectively at 5-minute intervals for 20 minutes. Treatments were administered 48 hours apart. RESULTS: Both treatments significantly reduced lameness scores at all evaluations, and the lameness scores did not differ significantly between the treatment groups. CONCLUSIONS: The effect of 0.5 mL of 2% mepivacaine HCl administered over each palmar digital nerve as an ASNB on lameness caused by digital pain did not differ significantly from the effect of 2.5 mL. CLINICAL RELEVANCE: The volume of a local anesthetic for an ASNB, adequate to ameliorate digital pain, is less than that commonly recommended. A lower volume might more specifically localize the site of pain to the digit, but this supposition remains to be investigated.