THE EFFECTS OF ADRENERGIC AND ADRENOLYTIC AGENTS ON THE APPEARANCE OF CARDIAC ARRHYTHMIAS DURING EXPERIMENTAL HYPOTHERMIA,

The object of this study was to compare the influence of the adrenergic drugs epinephrine and norepinephrine and the adrenolytic drug phentolamine on the course of cardiac arrhythmias and the terminal temperature during progressive hypothermia. Norepinephrine infused intravenously after cardiac temperature fell to 25 C or after systolic blood pressure fell to 100 mm Hg was successful in delaying the severe hypotension seen in control animals at temperatures below 25 C. Furthermore sinoauricular arrest and ventricular fibrillation were signigicantly delayed in appearance in animals so treated. Epinephrine was similarly successful in maintaining blood pressure but less effective, in doses used, in delaying the appearance of ventricular fibrillation. Phentolamine was without significant effect on heart rate, blood pressure, and terminal temperature.