Anesthesia and the leucocyte.

Effective inhibition of cell division by anesthetics occurs only when cells are exposed to concentrations more than twice those required for anesthesia. Neutropenia following prolonged inhalation of nitrous oxide seems to be caused by a different mechanism, in which the cobalt in B12 is oxidised to the trivalent form by chemical reaction with nitrous oxide. B12 is thereby inactivated and this interferes with folate metabolism and thymidine synthesis: the effect may be detected after only a few hours in vivo exposure of mammals to 50% nitrous oxide. Unlike lymphocytes, the random motility of human neutrophils is not decreased by in vitro exposure to concentrations of halothane required for anesthesia. Similarly there is no effect on chemotaxis to casein and phagocytosis with exposure up to 2% halothane.