Halothane Hepatitis Without Halothane: Role of Inapparent Circuit Contamination and Its Prevention

Abstract

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.

Neonatal anaesthesia

“…55 Whereas with morphine, which has a low fat solubility, a proportionally higher amount of morphine would cross into the brain of a newborn compared to an older child, simply because of the immaturity of the blood brain barrier. 56 Studies have shown that the peak pharmacodynamic effects of benzodiazepines are also directly proportional to fat solubility; the peak EEG effect of diazepam is nearly three times faster than that of midazolam. 57,58 A common misconception is the reverse, i.e.…”

Halothane and Hepatitis

“…For the patient who has had unexplained jaundice following a previous halothane anaesthetic, it is crucial that a halothane-free anaesthetic machine is used, since it has been shown that sufficient amounts of the drug can be released from the rubber tubing when another anaesthetic agent is used to sensitise such patients (Varma et al 1985). Current evidence also suggests that other halogenated anaesthetics should not be used.…”

Halothane and the Liver—the Present Situation

“…Other factors suggestive of possible patients at risk include those who are female and obese, with a history of allergy or eczema. In this context it should be realized that enough halothane may contaminate the conventional anaesthetic machine so that when a 'non-halothane' anaesthetic is given, enough halothane may be released from the tubing to cause a hepatitis (9). Thus ideally, a halothane-free machine should be used in such patients.…”