240 



INFLUENCE OF TEMPERATURE ON BIOLOGICAL SYSTEMS 



HYPOTHERMIA AND ASPHYXIAL SURVIVAL 



As a result of studies on newborn rats and puppies, Hirawich concluded 

 that poikilothermia is an important factor in the high degree of resistance 

 to anoxia shown by mammalian fetuses (91, 66). He did not, however, 

 suggest the trial of hypothermia as a means of increasing asphyxial 

 resistance. Neither did van Harreveld and Tyler (83) even though they 

 demonstrated that in cats there was less injury to the spinal cord after 

 120 minutes of asphyxia at 27° than after only 35 minutes at normal 

 temperatures. 



NEONATAL GUINEA PIGS 

 T. O. D. 



▲ Sherfett Survival 

 ▼ Longest Survival 

 O Means 



X 



A. 



100 ISO 200 250 300 350 400 450 500 550 600 650 



Fig. 1. Time of death of 205 neonatal guinea pigs exposed to 95% N^ + 5% CO^ at 

 different body temperatures. Data from table 1, Miller and Miller, 1954. 



In our early experiments it was found that the time of death (T.O.D.) 

 of newborn guinea pigs exposed to 95% N2 + 5% CO2 was increased 

 by reduction of body temperature and that cooled animals could recover 

 completely from exposures which were lethal for warmer littermates (117). 

 Since the implications of these findings were completely contrary to 

 standard practice for the treatment of shock and asphyxia of the new- 

 born, more extensive studies were made with hundreds of animals (127, 

 121, 122). The temperature range of the T.O.D. experiments was extended 

 from lethal heat to lethal cold in a series of 205 animals exposed until 

 death. In order not to complicate problems of interpretation, no attempts 

 were made in this study to counteract these secondary effects of hypo- 

 thermia, even though it was obvious that many of the animals that died 



