VOLATILE METABOLITES AND DECOMPOSITION PRODUCTS OF HALOTHANE IN MAN

The presence of two volatile halothane metabolites, 2 chloro 1,1,1 trifluoroethane (CF3CH2Cl) and 2 chloro 1,1 difluoroethylene (CF2 CHCl), and a metabolite decomposition product, 2 bromo 2 chloro 1,1 difluoroethylene (CF2CBrCl), were identified by gas chromatography mass spectrometry in exhaled gases of 16 patients anesthetized with halothane in nonrebreathing, semiclosed and totally closed anesthesia circuits. No significant differences in concentrations of CF3 CH2C1 and CF2CHCl were found relative to the anesthesia circuits used. CF2CBrCl could not be identified in the expired gases of patients anesthetized with a nonrebreathing circuit (Bain), but was present in gases recovered from both semiclosed and totally closed circuits. Under totally closed circuit rebreathing conditions, the concentration of CF2CBrCl increased 4-5 ppm, indicating significant breakdown of halothane by the soda lime. Possible pathways for formation of the two metabolites and the metabolite decomposition product are presented, as well as clinical implications of these findings.