[Cardiac arrhythmia in dogs under the action of adrenaline and difluorodichloromethane (FC 12)].

Inhalation of gas mixtures containing different concentrations of FC 12 by anesthetized and normally oxygenated dogs produces blood levels of FC 12 which are stable and proportional to the rate of FC 12 in the mixture. From the arterial concentration of 40 microgram/ml FC 12 (5 % FC 12 mixture) and over, FC 12 alone causes effects proportional to doses: arterial pressure decrease with tachycardia. At high rates of FC 12 tachypnoea and slight morphological alterations of the electrocardiogram can be recorded. Arhythmia never occurs under the action of FC 12 alone even at maximum arterial concentration reached here : 230 microgram/ml (40 % FC 12 mixture). Recorded disturbances are always reversible. The intravenous perfusion of epinephrine alone evokes the appearance of premature contractions at the only dose of 5 microgram/kg/mn. The presence of FC 12 in blood conjoined with epinephrine induces the inhibition of the hypertensive action of epinephrine at high concentration and lowers the arhythmogenic threshold. The dog is clearly more sensitive than the rabbit to the arhythmogenic action of epinephrine and FC 12. The required rates of epinephrine and FC 12 validate the hypothesis of cardiac sensitization by FC 12 to the arhythmogenic action of circulating adrenaline to explain the cases of sudden "sniffing" deaths in man.