Cardiovascular responses to an acute volume load in deep hypothermia.

Intravenous administration of warm fluids is used clinically as first aid either alone or as a contributing method, to rewarm hypothermic patients back to normal body temperature. The aim of this study was to determine the effects of an acute volume load in hypothermic conditions on the canine circulatory system. Cardiac catheterization was performed on 18 anaesthetized beagle dogs. Eleven of them were cooled and at a body temperature of 25 degrees C they received 40 ml.kg-1 dextran administered intravenously. The control group received dextran at normal body temperature. During cooling the body from 37 degrees C down to 25 degrees C most of the volume load escaped from the circulation due to extravazation. During rewarming, the opposite effect could be seen and the volume load persisted up to 29 degrees C and signs of cardiac decompensation were observed. According to these results, the intravenous administration of warm fluids to rewarm hypothermic patients should not be used routinely when hypovolaemia is the only result of hypothermia.