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.
Authors: Robert C Cole, Fred J DeGraves, Jessica Brown, John Schumacher
Journal: American journal of veterinary research
Summary
# Editorial Summary: Minimalist Mepivacaine Dosing for Abaxial Sesamoid Nerve Blocks When diagnosing digital lameness, abaxial sesamoid nerve blocks (ASNBs) remain a cornerstone technique, yet conventional practice has relied on relatively large anesthetic volumes without robust evidence supporting these recommendations. Cole and colleagues conducted a crossover trial on six lame horses, comparing the analgesic efficacy of 0.5 mL versus 2.5 mL of 2% mepivacaine administered over each palmar digital nerve near the proximal sesamoid base, with objective gait analysis using an inertial sensor system at baseline and at 5-minute intervals over 20 minutes. Both treatment volumes significantly ameliorated lameness scores throughout the evaluation period, with no statistically significant difference between the two dosing protocols. These findings suggest that current practice may employ substantially greater anesthetic volumes than necessary to achieve adequate pain relief in digital structures, potentially raising questions about localisation precision during diagnostic nerve blocks and the economic efficiency of nerve block procedures. Clinicians might consider whether reducing ASNB volumes could improve diagnostic specificity by better distinguishing digital pain from proximal structures, though the authors acknowledge this possibility requires further investigation; in the interim, practitioners have evidence that effective pain relief can be achieved with a five-fold reduction in standard mepivacaine dosing.
Read the full abstract on PubMed
Practical Takeaways
- •You can safely reduce mepivacaine volume to 0.5 mL per nerve for abaxial sesamoid blocks while maintaining effectiveness for digital pain diagnosis and treatment
- •Using lower anesthetic volumes may improve localization of pain to the digit, potentially making diagnostic blocks more specific
- •This finding challenges the conventional wisdom of using higher volumes and could reduce cost and anesthetic exposure in routine practice
Key Findings
- •Both 0.5 mL and 2.5 mL mepivacaine significantly reduced lameness scores at all evaluation time points
- •No significant difference in lameness reduction between 0.5 mL and 2.5 mL treatment groups
- •Abaxial sesamoid nerve block with reduced volume (0.5 mL) proved as effective as standard volume (2.5 mL) for digital pain