342 



PHYSIOLOGY OF INDUCED HYPOTHERMIA 



8.5 



40 

 TEMP. 



30 20 10 



COOLING 



20 30 



RE WARMING 



40 



Fig. 2. — Blood pH in dogs breathing a mixture of 5 per cent carbon dioxide in oxygen. 

 (By permission of Surgery, Gynecology and Obstetrics.) 



Resuscitation of dogs from temperatures below 10° C. has been impossible on 

 oxygen alone. With the high pH's that occur mo.st of the animals fibrillated at low 

 temperatures. Some of them had a continued heartbeat, especially the yoimger ones. 

 Here age differences complicate matters, but in any case, none of them survived the 

 complete experiment. 



When 5 per cent carbon dioxide in oxygen was used with the same respiratory 

 rate (about 13 respirations per minute), the pH was maintained at a level slightly 

 below normal. All the young dogs could l)e cooled to below 10° C. with the heart 

 continuing to beat and without fibrillation, though they could not be resuscitated. 

 The adult animals, if given only 5 per cent carbon dioxide, still developed ventric- 

 ular fil)rillation, though at lower temperature levels. By giving them 10 ])er cent 

 carljon dioxide, however, nine out of twelve were cooled to 10° C. or lower without 

 fibrillation, though they still were not resuscitated. In contrast to this, with oxygen 

 alone all adult animals fil)rillatcd at temperatin"e levels between 19° and 23° C, as 

 other investigators have shown. 



When the plf was raised to a high Icxi'l at 20° C. througli adding oxygen as 

 shown in figiu'e 3, 45 per cent of 38 animals went into cardiac standstill. The rest 

 went into ventricular fibrillalion or their hearts continued to beat. Those which fibril- 



