Halothane hepatitis without halothane: role of inapparent circuit contamination and its prevention

Halothane and other halogenated anesthetic agents are liquids which are highly soluble in rubber and plastic materials widely used as components of anesthesia machines. These agents must be administered using machines equipped with vaporizers. We report a patient with a past history of halothane hepatitis in whom recurrence was suspected despite the fact that halothane had been avoided purposely during the subsequent operation. Circumstances led us to believe that inapparent circuit contamination of vaporizer-equipped anesthesia machine with halothane may be responsible for the inadvertant rechallenge and recurrence of halothane hepatitis. Vaporizer-equipped machines were tested for inapparent contamination with halothane and enflurane using Perkin-Elmer mass spectrometer. Oxygen alone was passed through the anesthesia circuits, and gas in the efferent limbs of the machines was tested for halothane (in eight machines) and enflurane (in two machines) which were found in various concentrations in all machines so tested. Our findings suggest that inapparent contamination may be widely prevalent in vaporizer-equipped anesthesia machines. The validity of this conclusion was confirmed in five patients with previous diagnosis of halothane hepatitis who subsequently underwent operations under general anesthesia during which machines never equipped with vaporizers were successful in preventing recurrence of hepatitis. We conclude that patients with a prior history of halothane hepatitis are at risk of inapparent circuit contamination-induced recurrent hepatitis. Unless such contamination can be confidently excluded, vaporizer-equipped machines should not be used to administer general anesthesia in these susceptible patients.