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.

Abstract

OBJECTIVE: To compare a 2% lidocaine solution containing 5&#xa0;&#x3bc;g/ml (1:200&#x2009;000) epinephrine with 2% mepivacaine for reducing lameness in horses after use in proximal nerve blocks. STUDY DESIGN: Experimental randomized crossover. ANIMALS: Six adult horses with naturally occurring forelimb lameness. METHODS: Horses were evaluated using an inertial gait sensor system. Lameness was measured as a vector sum (VS). Following baseline lameness examination, median and ulnar nerve blocks were performed with lidocaine/epinephrine (0.5&#xa0;mg epinephrine added to 50&#x2009;ml of 2% lidocaine immediately prior to administration) or an equal volume of 2% mepivacaine. Horses were trotted at 5&#xa0;min and then at 30 min intervals for 150&#x2009;min. After 24&#x2009;h, nerve blocks were repeated using the other local anesthetic. Data were evaluated using linear models. RESULTS: The reduction in the VS did not differ after nerve blocks with lidocaine/epinephrine or mepivacaine (P&#xa0;=&#xa0;.791). Mean time to VS <8.5&#x2009;mm (n&#xa0;=&#xa0;5) was 5 and 9.6&#xa0;min for lidocaine/epinephrine and mepivacaine, respectively. For one horse, VS was not reduced to <8.5&#x2009;mm with either treatment (this horse had the highest VS before treatments were administered). The decrease in VS to <8.5&#x2009;mm lasted for 150&#x2009;min in both treatment groups. CONCLUSION: The outcomes of the median and ulnar nerve blocks performed with 2% lidocaine with epinephrine did not differ from blocks performed with 2% mepivacaine. CLINICAL RELEVANCE: Two percent lidocaine with epinephrine may serve as an adequate replacement for proximal nerve blocks when mepivacaine is unavailable.