EFFECTS OF HYPOTHERMIA ON GENERAL METABOLISM* 



STEVEN M. HORVATH and G. B. SPURR 



Survival of isolated cells, tissues and small organisms after cooling and storage 

 at very low temperatures, close to absolute zero, has been frequently reported. In 

 contrast, adult intact animals apparently are sensitive to moderate reductions in body 

 temperature. In dogs and man body temperatures below 25° C. usually contraindi- 

 cate surgical procedures because of the risk of ventricular fibrillation and cardiac 

 arrest. However, temperatures as low as 18-19° C. have been induced in dogs and 

 man with survival.^' -■ ^ Rodents have l)een frequently cooled and successfully 

 revived from body temperatures of approximately zero.^* °' *^ Recently Gollan^ using 

 extra-corporeal cooling, oxygenation and re warming of the blood has revived dogs 

 with body temperatures as low as 0° C. and in cardiac arrest for one hour. 



Marked species variation in the response to hypothermia has been demonstrated.^ 

 This has been expressed for some species as mean duration of survival time conse- 

 quent to exposure to a constant air temperature of —35° C. Under these conditions 

 the mouse survives 0.4 hours, the rat 0.75 to 2.0 hours, the rabbit 3.5 to 6.5 hours, 

 and the pigeon 22 to 78 hours. Smaller members of a species respond better to a 

 lowering of their body temperature than do the larger ones. Similarly, a significant 

 difference was noted in the lethal temperature of adults and infants of various 

 species.® Maquire and AIerendino^° have also remarked upon the greater tolerance 

 of the younger animals. Furthermore, they reported that cardiac arrest occurred 

 in their juvenile dogs while ventricular fibrillation occurred in the adults. All of 

 these observations are suggestive of the complexity of an organism's response to 

 lowered body temperature. 



Every biological process depends upon a series of consecutive reactions, each 

 characterized by a definite temperature coefticient and each becoming the limiting- 

 factor or the master process at a definite temperature. This implies that certain 

 reactions have a more significant influence at some temperature ranges than others. 

 This does not deny the importance of other factors such as the products of reactions, 

 the chemical environment or the availability of the substrate on chemical or biologi- 

 cal processes or responses. In fact, these other factors are to some extent deter- 

 mined by temperature. All of these influences can be summed in the Arrhenius 

 formula, wherein 



^'-^\r\ t„t, ; 



This equation reflects the underlying metabolic chemical reactions. Activation ener- 

 gies calculated from this formula are of the order of 11,500 and 16,500 calories and 

 are those associated with cell respiration corresponding to hydroxyl and iron cata- 

 lyzed systems respectively. Therefore, it is evident that oxygen is a limiting factor 

 and temperature a controlling factor in the response of the cell and the organism to 

 their environments. 



Efficiency of cellular function is determined by their metabolic composition con- 



* Aided by a grant from the Josiah Macy, Jr. Foundation. 



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