Fat metabolism in elderly patients with severe hypothermia

Elderly patients with accidental hypothermia (core temperatures 25.0-35.5 degrees C) have been studied to determine the effect of low temperature on energy metabolism. The respiratory exchange ratios were low (median 0.75). Concentrations of plasma glycerol, non-esterified fatty acids and ketone bodies were high, and, except in the case of glycerol, rose with the duration of the hypothermia. Plasma glucose concentrations were often high but extremely variable. Arteriovenous differences across the forearm showed net release of glycerol and extraction of ketone bodies. Despite the hypothermia the mean extraction ratios for acetoacetate and 3-hydroxybutyrate were very similar to published values in normal, fasting, euthermic subjects. It was concluded that, in agreement with other work showing inhibition of glucose utilization at low temperature, fat is the main fuel used at very low body temperatures.