Effect of Hypothermia on the Tolerance of Dogs to Digitalis

The tolerance to digitalis was studied in eight dogs during hypothermia and compared to that of six normothermic animals. The average lethal dose of Digoxin for the dog under hypothermia was found to be approximately double that of the normothermic dog. Thus, hypothermia significantly increases the tolerance of the drug. The possible explanation for this finding is discussed. It appears that hypothermia, by its direct effect on myocardial metabolism, might counteract the toxic effects of digitalis. Potassium, affected by both hypothermia and digitalis, is also a possible factor. The clinical implications of this finding are discussed.