Responses of Dogs to Hypothermia

Abstract

Prolonged, stable low body temperatures were produced for an average of 10.1 hours (1-34 hours) in 12 of 24 experiments on anesthetized dogs. An exponential relationship between the decreases in heart rate, pulmonary ventilation and O2 consumption and the reduction in the rectal temperature was observed, in agreement with van''t Hoff''s rule. Shivering increased pulmonary ventilation and O2 consumption without changing the nature of the dependence on body temperature although it altered the level of this dependency. The rectal temperature of the animals in which a stable low temperature was established fell more slowly than the rectal temperature of non-stable animals, because of a higher level of heat production at rectal temperature from 30.5[degree] to 24.5[degree]C. The ventilation equivalent showed no reproducible pattern of responses to the fall in rectal temperature. The cardiac and respiratory rates, pulmonary ventilation, ventilation equivalent and O2 consumption were less constant than the rectal temperature during the period of stability. The inability to control these factors may have been the limiting element in this hypothermic preparation.