Inhibition by halothane, but not by isoflurane, of oxidative response to opsonized zymosan in whole blood

In an attempt to clarify some apparent discrepancies in reports of the effects of anesthetic agents upon granulocyte function, we studied the effects of halothane and isoflurane, using techniques that allowed us to perform the assays in whole blood and in sealed vials to prevent volatile gas evolution; assay gas concentrations were measured, rather than inferred. Chemiluminescence, superoxide production, and hydrogen peroxide production were assessed after presentation of opsonized zymosan as a phagocytic stimulus. Incubation with halothane led to a highly statistically significant dose-related inhibition of Chemiluminescence (maximum 66%), H₂O₂ production (67%) and ·O₂^- production (61%), within the concentration range observed in blood from patients undergoing general anesthesia. In contrast, the presence of isoflurane led to no statistically significant changes in any of the functions measured. Cells harvested from patients undergoing elective halothane anesthesia showed the same functional inhibition, but for quantitative differences likely due to the inability to control for dilution effects in clinical samples. It has been suggested that halothane anesthesia may be associated with excess mortality in septic patients; although the results we report are readily reversible, their presence during a prolonged anesthesia could be harmful in a patient who is not immunologically normal and/or who is already infected. Careful clinical trials will be necessary to determine if isoflurane is a superior agent in this context.