Cardiovascular Response to Hypothermia: Effect of Cold Acclimatization

¹ From the Department of Physiology, Arctic Aeromedical Laboratory, APO 731, Seattle, Washington

The cardiovascular response to hypothermia was studied in dogs which had been exposed continuously to sub-zero arctic temperatures for a period of 1–4 weeks. All dogs exposed in this fashion showed a significantly lower terminal rectal temperature than unexposed control dogs. In addition, the incidence of ventricular fibrillation was reduced in direct proportion to the exposure period. Acclimatization to cold appeared complete in dogs exposed for a period of 4 weeks. In this group of animals, the frequency of ventricular fibrillation was reduced to 9% as compared to an incidence of 96% in the control dogs. The process of acclimatization occurred with extreme rapidity. Dogs which were deemed fully acclimatized, became deacclimatized after 5 days in a warm environment. Both the frequency of ventricular fibrillation and the mean terminal rectal temperature of this group were the same as that in the control unexposed group.