Influence of Induced Hypothermia on Digitalis Toxicity

PREVIOUS studies on the effect of digitalis on the hypothermic heart have indicated that the arrhythmic effects of hypothermia and digitalis are antagonistic. Those experiments were primarily intended to study the effect of digitalization on hypothermia using pharmacological doses of digitalis. In the experiments reported herein, the procedure was reversed in that it was thought to be of value to investigate the possible use of hypothermia as an antagonist of digitalis toxicity. For this purpose dogs injected with toxic doses of ouabain were subsequently cooled and stabilized in a state of moderate hypothermia at body temperatures of 28 to 31 C. where spontaneous fibrillation (due to hypothermia) does not occur. The clinical problem of digitalis toxicity is too well known and needs no further comment. However, it should be emphasized at this point that digitalis-induced arrhythmias are only a prelude and warning of impending death due to ventricular fibrillation. Yet arrhythmias and ventricular fibrillation are not entirely dependent on the same mechanisms, so that protection from arrhythmias is not necessarily associated with protection from death due to ventricular fibrillation or possibly cardiac standstill. It is essential, therefore, to determine whether hypothermia could alter the lethal as well as the arrhythmic effects of digitalis.