Comparison of 2% mepivacaine and a solution of 2% lidocaine/epinephrine administered for median and ulnar nerve blocks in horses with naturally occurring forelimb lameness.
Authors: Boorman Sophie, DeGraves Fred, Schumacher John, Hanson Russel Reid, Boone Lindsey H
Journal: Veterinary surgery : VS
Summary
# Editorial Summary Proximal median and ulnar nerve blocks are commonly used diagnostic tools in equine lameness evaluation, but local anaesthetic availability can be inconsistent in practice. This randomised crossover study compared the efficacy of 2% lidocaine with low-dose epinephrine (5 µg/ml) against 2% mepivacaine in six horses presenting with naturally occurring forelimb lameness, using inertial measurement sensors to quantify gait changes with precision. Both anaesthetics produced equivalent reductions in lameness (measured as vector sum), with lidocaine/epinephrine achieving diagnostic threshold (vector sum <8.5 mm) slightly faster at 5 minutes compared to mepivacaine at 9.6 minutes, and both maintaining diagnostic blockade for the full 150-minute assessment period. The single horse that failed to achieve adequate blockade with either agent had the highest baseline lameness scores, suggesting individual factors may influence response independent of anaesthetic choice. For practitioners, this finding offers reassurance that lidocaine supplemented with epinephrine provides a reliable alternative when mepivacaine supply is limited, particularly given the faster onset time, though availability of either agent should be verified before diagnostic procedures.
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Practical Takeaways
- •Lidocaine with epinephrine is an effective substitute for mepivacaine in median and ulnar nerve blocks when mepivacaine is unavailable
- •Both local anesthetics produce similar clinical outcomes and duration (150+ minutes), supporting either choice based on availability
- •Response timing is slightly faster with lidocaine/epinephrine (5 vs 9.6 minutes), but both are clinically acceptable for lameness evaluation
Key Findings
- •Reduction in lameness vector sum did not differ between 2% lidocaine/epinephrine and 2% mepivacaine nerve blocks (P = 0.791)
- •Mean time to clinically significant lameness reduction (<8.5 mm) was 5 minutes for lidocaine/epinephrine versus 9.6 minutes for mepivacaine
- •Both treatments produced lameness reduction lasting 150 minutes in all responsive horses
- •One horse with highest baseline lameness did not achieve clinically significant reduction with either treatment