238 



INFLUENCE OF TEMPERATURE ON BIOLOGICAL SYSTEMS 



FACTORS AFFECTING TOLERANCE OF HYPOTHERMIA 



Below is a list of factors known to influence the lower limits of 

 survival under hypothermia. 



Age. In all species studied thus far, the resistance to hypothermia is 

 greater in the newborn than adult of the same species (60, 163, 38, 62, 

 1, 2). These studies include the hamster, rat, rabbit, cat, dog and guinea 

 pig. In table 1 the lethal temperatures for non-narcotized adults and 

 neonatal infants of seven species of mammals are listed. As may be seen, 

 there are no figures for pups and human babies, but recoveries from 



temperatures well below 20° are known. Unless the human baby is an 

 exception to the rule, the margin of safety for the use of cooling should 

 be greater than it is in the case of adults. Since in the operating room 

 poor risk patients can be safely cooled to 25°C (177), the probability 

 is that temperatures considerably lower are safe for the newborn. 



Narcosis. This factor, which is just beginning to be appreciated (121- 

 124) , explains many of the discrepancies in the results of different investi- 

 gators. For example, from the experiments at Dachau, one would conclude 

 that lethal temperatures for man are between 26° and 27°C, with an 

 occasional individual who can tolerate slightly lower temperatures. In 

 these experiments, the lowest temperature from which recovery occurred 

 was 25.2°C (4). By contrast, Fay (64), who used hypothermia in combi- 



