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.

The research examined if different volumes of the local anaesthetic, mepivacaine, have varying effects on horse lameness due to digital pain. The study found no significant difference in lameness reduction between 0.5 mL and 2.5 mL of the medication, suggesting that a smaller volume than commonly recommended might be sufficient.

Study Design and Procedure

• Researchers used six horses affected by naturally occurring digital pain. A crossover study design was implemented, meaning each horse received both the 0.5 mL and 2.5 mL mepivacaine treatments at different times, with three horses in each treatment group.
• The lameness of the horses was evaluated via a motion-analysis system specifically designed for this purpose, called the “Lameness Locator”. This provided objective records of walking gait before and after the application of mepivacaine.
• This gait evaluation was repeated every five minutes for a total observation period of 20 minutes post-treatment. Treatments were given at intervals of 48 hours to avoid interference of effects.

Findings

• Both volumes of mepivacaine significantly decreased lameness scores across all assessment times, indicating the anesthetic’s effectiveness in relieving digital pain.
• No substantial difference was observed between the 0.5 mL and 2.5 mL treatments. Both volumes were able to reduce pain and subsequently lameness in the horses.

Implications

• The findings suggest that the appropriate volume of mepivacaine needed for effective digital pain management might be lower than what is widely recommended in the field.
• A smaller amount of anesthetic may lead to precise pain localisation to the affected digit, but more research is needed in this area.