ECG changes in benzene, toluene and xylene poisoned rats.

Electrical activity of the heart was studied in acute, subacute and chronic benzene, toluene and xylene poisoning by means of NEK-2 type apparatus in CFY male rats. In the early period of acute intoxication benzene and its methyl derivatives, injected either intraperitoneally or subcutaneously or administered by inhalation did not cause changes in the ECG. Intravenously injected toluene induced a rapid and permanent decrease in blood pressure, in higher doses respiratory paralysis. In acute inhalation toluene and xylene poisoning the anesthesia was followed by respiratory paralysis, bradyarrhythmia and asystole, while inhalation of benzene induced respiratory paralysis followed by ventricular fibrillation. Subacute poisoning with benzene, toluene and xylene caused disorders in repolarization and arrhythmia. The degree, incidence and development of these phenomena depended on the dose and the duration of exposure. The effect of benzene influencing ECG was appreciably more intensive than that of toluene or xylene. Owing to the high number of spontaneous ECG changes due to ageing, it is difficult to evaluate the effect of chronic exposure to the agents under investigation.