Metabolic Reduction in Hypothermia: Pathophysiological Problems and Natural Examples - Part 2

Abstract

As an example of spontaneous cooling in homeothermic organisms, hibernation of mammals is described. Based on the fact that all hibernators, at their regulated minimal body temperature, display a uniform turnover rate, related to body weight, the hypothesis is developed that cold tolerance of mammals is generally limited by a common specific minimal metabolic rate, which larger organisms, because of their lower basal metabolism, already attain in less profound hypothermia. The observation that there is, in natural lethargic states, a certain independence between metabolic rate and body temperature, subsequently leads to considerations on the presumable modulating influence exerted by the acid-base balance. Finally, referring to the time limitations of such adaptation strategies, the cold-induced disintegration of metabolic processes with differing temperature dependence is illustrated which, however, will be more pronounced in the intermediate temperature range than in lower cooling. Thus, despite a limited cold tolerance, an extremely profound hypothermia of short duration seems not altogether impossible even for large homeotherms, provided some adequate conditions of rewarming are observed.