pH adjustment schedule for the amide local anesthetics.

Several studies have indicated that the addition of sodium bicarbonate to solutions of local anesthetics to raise the pH closer to the pKa shortens the latency, increases the intensity, and prolongs the duration of the resultant neural blockade. However, the addition of too much bicarbonate will cause precipitation, and this may result in the injection of particulate free base along with the solution. The present study was carried out to determine the maximal amount of sodium bicarbonate that can be added to each of the amide local anesthetics without the formation of a precipitate, and, thus, to construct a pH adjustment schedule to simplify the alkalinization of local anesthetics in clinical practice.