Buffering mepivacaine with sodium bicarbonate speeds and potentiates analgesia of median and ulnar nerve blocks performed on horses.

The objective of this study was to determine if buffering mepivacaine HCL (mepHCl) with sodium bicarbonate (NaHCO3 ) would significantly decrease the time to onset of analgesia when performing median and ulnar nerve blocks in naturally lame horses. Median and ulnar nerve blocks were performed on the naturally lame limb of nine horses during two separate study periods, with a minimum washout period of three days between study periods. Nerve blocks were performed by administering mepHCl alone or mepHCl mixed with NaHCO3 (nine parts 2 per cent mepHCl to one part 8.4 per cent NaHCO3 ). Lameness was evaluated objectively using a wireless, inertial, sensor-based, motion analysis system (Lameness Locator) prior to the high regional nerve block and every five minutes following administration of the nerve block for 75 min. Resolution of lameness occurred earlier and was more profound for horses administered median and ulnar nerve blocks performed with mepHCl and NaHCO3 than when these nerve blocks were performed using only mepHCl.