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

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