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Accumulation and Persistence of Halothane in Adult and Fetal Rat Brain as a Result of Subanesthetic Exposure

Halothane (2-bromo-2-chloro1 , 1 , I-trifluroethane) is a relatively stable and useful anesthetic; however, it is not metabolically inert and consequently there may be undesirable circumstances of exposure. Many investigations have shown various effects of acute exposure to halothane on adult intermediary metabolism and on behavior. Of particular concern are effects of chronic, fetal exposure to trace amounts of halothane, as in the case of unborn offspring of operating room personnel (Van Dyke, 1978; Butcher, 1978). Many of these studies require cautious interpretation as effects are often demonstrated with chronic exposure regimes using doses much higher than actual occupational exposures; however, demonstrated effects include reduced fertility, survival, and growth (Cohen et al., 1971; Corbett, 1972; Bussard et al., 1974; Pope et al., 1978; Wharton et al., 1978), inhibition of DNA synthesis (Grant, 1973; Evenwel et al., 1976; Bandoh and Fujita, 1976; Sturrock and Nunn, 1976), pathological effects (Chang et al., 1974; 1976; Chang and Katz, 1976), decreased brain myelination (Wiggins et al., 1979), and abnormal behavior (Quimby et al., 1974; 1975; Smith et ai., 1978). Because of this current interest in the fetal toxicity of halothane, particularly to the developing nervous system, the present investigation was designed to compare the absorption and retention of halothane in fetal and adult (maternal) brain. We used a subanesthetic concentration (0.5%) that permits routine, accurate detection in tissues. Results show that fetal tissue values are comparable to maternal, and thus neither the interposition of a placenta between the two circulatory systems, nor the absence of detoxification capability in fetal liver has any significant effect on fetal halothane accumulation, or retention.