Alkalinization of mepivacaine for axillary block

We examined the onset and distribution of sensory blockade, the onset of motor blockade, and venous mepivacaine concentrations after axillary block with 1.25% mepivacaine with and without bicarbonate. There were no statistically significant differences between the alkalinized and placebo groups with respect to distribution of analgesia or anesthesia, time to onset of analgesia, or time to onset of paresis. However, alkalinization significantly decreased the time to onset of anesthesia in the medial cutaneous nerve of the forearm, the median nerve, and the ulnar nerve, as well as the time to onset of paralysis. Concentrations of mepivacaine in venous blood did not differ significantly. We conclude that alkalinized mepivacaine offers the advantage of quicker onset of more profound blockade in several terminal nerve distributions.