The preceding report (page 124) indicated that the use of chloroprocaine (2CP) for epidural anesthesia is not excessively hazardous if certain precautions are observed. We find in this report that 2CP is a safe local anesthetic drug. Severe neurodysfunction occurs in the isolated nerve when exposed to Nesacaine, the commercial 2CP preparation, which contains the additive sodium bisulfite (as an antioxidant) at low pH. We ascribe nerve function failure to the low intracellular pH resulting from SO2 diffusion into the cell followed by hydration to H2SO3. The molecular SO2 is liberated from bisulfite at low pH. The SO2 concentration is dependent on the bisulfite concentration and the degree of pH depression. Application of the factors presented above, plus the factor of spinal compliance presented in the previous report, explains most of the paradoxical findings reported from other laboratories in the “chloroprocaine controversy.”
- Bisulfite oxidation/reduction
- Biochemical effects
- Effect of hydrogen ion concentration
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Supported in part by NIH Grant #R01/GM 30160‐02 and by a grant from Astra Pharmaceutical Products Corporation.
Address reprint requests to Dr. Gissen: Department of Anesthesia, Brigham and Women's Hospital, 75 Francis St., Boston, MA 02115.