Decomposition of Volatile Anesthetics in Soda Lime

Abstract

Soda lime mediated decomposition products of volatile anesthetics--halothane, enflurane, isoflurane and sevoflurane--and the degree of degradation, toxicity and concentration in an anesthetic circuit equipped with a model lung are described. These anesthetics undergo decomposition by soda lime as follows: halothane decomposes to yield difluorochlorobromoethylene and trifluorochloroethane; enflurane decomposes to yield l-chloro-l,2-difluorovinyl difluoromethyl ether; isoflurane decomposes to yield 2,2-difluoro-l-chlorovinyl difluoromethyl ether and fluoroform; sevoflurane decomposes to yield fluoromethyl 2,2-difluoro-l-(trifluoromethyl)vinyl ether, fluoromethyl 2-methyl-2,2-difluoro-l-(difluoromethylene)ethyl ether, two isomers of fluoromethyl 2-methoxy-2-fluoro-l-(trifluoromethyl)vinyl ether and fluoromethyl 2,2-difluoro-l-(difluoromethoxy ethyl)vinyl ether. Almost all degraded compounds of these volatile anesthetics are produced by elimination of hydrofluoride from adjacent carbon atoms by soda lime.