Letter: Occupational hazard of halothane

Occupational exposure to volatile anaesthetics: epidemiology and approaches to reducing the problem

Long term occupational exposure to trace concentrations of volatile anaesthetics is thought to have adverse effects on the health of exposed personnel. In contrast with halothane--an agent likely to cause mutagenic effects and proven to be teratogenic--isoflurane and enflurane have not so far been proved to have adverse effects on the health of personnel exposed long term. Data on the newer agents sevoflurane and desflurane are limited. Since possible health hazards from long term exposure to inhalational anaesthetics cannot yet be definitively excluded, many Western countries have established limits for exposure. These usually range from 2 to 10 ppm as a time-weighted average over the time of exposure. A number of investigations have demonstrated that, in operating theatres with modern climate control and waste anaesthetic gas scavenging systems, occupational exposure is unlikely to exceed threshold limits. However, occupational exposure from the use of volatile agents in operating theatres with poor air control--especially during bronchoscopy procedures in paediatric patients--remains a source of concern. This also holds true for both postanaesthesia care units (PACU) and intensive care units (ICU) lacking proper air conditioning and waste gas scavengers. To minimise occupational exposure to volatile anaesthetics, all measures must be taken to provide climate control and properly working scavenging devices, and ensure sufficient personal skill of the anaesthetist, e.g. during inhalational mask induction. Furthermore, low-flow anaesthesia should be used whenever possible. The sole use of intravenous drugs such as propofol instead of volatile agents, were this possible, would eliminate occupational exposure, but may result in environmental pollution by toxic metabolites (e.g. phenol).

Hepatic injury in rats due to prolonged sub-anaesthetic halothane exposure

Fischer-344 rats of both sexes were exposed to halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) at a concentration of 50 p.p.m. for twelve weeks. During the course of the experiment, weight gain of both sexes was depressed and serum alanine aminotransferase activities were elevated, compared to control animals. The temporal pattern of alanine aminotransferase elevation differed between the sexes. After 12 weeks of exposure, liver/body weight ratio was increased in both sexes, and pathological changes were observed in their livers. Livers of all halothane-exposed animals showed focal liver cell necrosis, considerable lobular disarray and occasional mitoses. Many liver cells showed fatty change. None of these changes were observed in any control animals. These results indicate that prolonged exposure to a low concentration of halothane caused mild liver damage with regeneration. This finding may be of significance to humans occupationally exposed to halothane.