In vitro antiseptic effects on viability of neuronal and Schwann cells

Chlorhexidine is recommended by several anesthesiology societies for antisepsis before regional anesthesia, but there is concern it may be neurotoxic. We evaluated the cytotoxicity of chlorhexidine and povidone-iodine in human neuronal and rat Schwann cells.

Human SH-SY5Y neuroblastoma and rat RSC96 Schwann cells were incubated with serial dilutions of 2% chlorhexidine gluconate and 10% povidone-iodine for 10 minutes, and viability was assessed with the MTT colorimetry assay and a fluorescent assay using calcein and ethidium. Cell morphology during antiseptic incubation was observed under light microscopy. To estimate the amount of antiseptic a needle carries through tissues, tritium radioactivity was measured in an animal injection model.

Chlorhexidine at all tested concentrations significantly decreased viability compared with controls in both SH-SY5Y and RSC96 cells (P < 0.001). Povidone-iodine significantly decreased viability for both cells at concentrations of 0.2% or higher (P < 0.001). At the same dilutions of 1:200, 1:150, and 1:100, chlorhexidine was more cytotoxic than povidone-iodine for both cells (P< 0.001). During chlorhexidine treatment, both cell types became rounded and shriveled. Less dramatic changes were observed with povidone-iodine. In the injection model, 1.75% ± 1.29% of the maximum amount of radioactive contamination was carried through tissues.

Chlorhexidine gluconate and povidone-iodine were cytotoxic to SH-SY5Y (neuronal) and RSC96 (Schwann) cells. Chlorhexidine was more potent than povidone-iodine at more dilute concentrations. However, the toxicity of the two was not different at concentrations used clinically. When using either of these agents for antisepsis before regional anesthesia, it is prudent to allow adequate drying time after application.