The role of 2-chloroprocaine and sodium bisulfite in rat sciatic nerve edema

In order to evaluate the possible mechanisms of local anesthetic toxicity, the rat sciatic nerve was exposed to various solutions including Nesacaine (containing the antioxidant sodium bisulfite), 2-chloroprocaine in the Nesacaine vehicle (0.2% sodium chloride), 0.2% sodium bisulfite in 0.2% sodium chloride, or 0.2% sodium chloride alone. All solutions were pH balanced between 2.9 and 3.2. Forty-eight hours (h) following extraneural administration of 1 ml volumes, significant edema was produced by all solutions containing 3% 2-chloroprocaine, but not with 0.2% bisulfite in sodium chloride or with sodium chloride alone. Intrafascicular administration of five to ten microliter volumes of these solutions produced edema at 48 h in all cases, but the highest levels were observed with Nesacaine and the lowest levels with 0.2% bisulfite. The results of this study implicate the local anesthetic 2-chloroprocaine in the production of nerve edema, which is inconsistent with other reports that the toxicity of Nesacaine-CE can be attributed to the antioxidant bisulfite.