thiopental and methyl-bromide

Systemic methyl bromide (CH3Br) poisoning with signs and symptoms of varying severity developed in nine greenhouse workers after acute inhalational exposure on two consecutive days. Measurements of CH3Br, carried out at the site within hours after the accident, suggest that exposure on the second day may have been in excess of 200 ppm (800 mg/m3) CH3Br. All workers were admitted for observation. Seven of them were discharged after an uneventful overnight observation and residual symptoms, if any, subsided within three weeks of the accident. Two patients needed intensive care for several weeks because of severe reactive myoclonus and tonic-clonic generalised convulsions. These conditions were unresponsive to repeated doses of diazepam, clonazepam, and diphenylhydantoin but could be suppressed effectively by induction of a thiopental coma that had to be continued for three weeks. In some of the patients prior subchronic exposure to CH3Br, as shown by their occupational histories and high serum bromide (Br-) concentrations, is likely to have been a factor contributing to the severity of their symptoms. A direct association between serum Br- concentrations and the severity of neurological symptoms, however, seemed to be absent. An on site investigation into the circumstances leading to the accident showed the presence of an empty and out of use drainage system that covered both sections of the greenhouse. This was probably the most important factor contributing to the rapid and inadvertent spread of CH3Br.

Topics: Accidents, Occupational; Adult; Agricultural Workers' Diseases; Female; Fumigation; Humans; Hydrocarbons, Brominated; Male; Occupational Exposure; Thiopental

Changes in locomotor activity, body temperature, and body weight gain, and the enhancement of thiopental-induced sleep were investigated in rats as indices of the functional changes in the CNS caused by methyl bromide (CH3Br) exposure. The correlations of these behavioral changes with CH3Br metabolism are discussed. The LC50 value and its 95% confidence limits for an 8-hr exposure of CH3Br was 302 ppm (267-340) ppm. Effects were examined following exposure to 63, 125, 188, or 250 ppm CH3Br for 8 hr. CH3Br concentrations as low as 63 ppm remarkably enhanced the sleep-inducing potency of thiopental, but CH3Br exerted no effect on thiopental metabolism. The body temperature and body weight gain were decreased at exposure to concentrations of 125 ppm or higher, and locomotor activity was reduced at 188 ppm or higher. These effects were reversible and, at 24 hr after the exposure, locomotor activity and body temperature were almost the same as in control rats. In a time-course study of CH3Br, bromine, and methyl alcohol, CH3Br was rapidly eliminated from rat tissues following the cessation of exposure, with a half-life of about 30 min in the early post-exposure period. In contrast, the elimination rate of bromine was very slow, with a half-life about 5 days. The methanol amount was below that reported to induce the changes in CNS functions. These results suggest that the CNS depression caused by CH3Br exposure may be due to the CH3Br molecule or the methyl moiety incorporated into tissues and may not be attributable to bromine or methanol. A linear relationship was obtained between bromine amounts in blood and the exposure concentration or duration. This result suggests the possibility that the extent of CH3Br exposure may be estimated from the bromine quantities in blood.

Topics: Animals; Atmosphere Exposure Chambers; Body Temperature; Chromatography, Gas; Drug Interactions; Half-Life; Hydrocarbons, Brominated; Injections, Intraperitoneal; Lethal Dose 50; Male; Motor Activity; Rats; Rats, Inbred Strains; Regression Analysis; Sleep; Thiopental; Tissue Distribution