272 



PHYSIOLOGY OF INDUCED HYPOTHERMIA 



f S:::::::::i::;;.v;;:i::^ 



•=p<2rfas0d. sid(2 



VENA CftVA OCCLUDED- 



■CHEST CLOSED ».l«-5 -> 



42''WATER 3RTH 



IZOr' 

 ^ cs 90-r 

 ^^ 60f 



^^ Li 



-I 1- 



.^: 



10 



15 20 



25 



30 



35 40 45 50 55 60 65 70 



MIN.-- 5 



Fig. 1. — Pulse, blood pressure and differential temperatures of a dog during 15 minutes of 

 perfusion cooling, 30 minutes of occlusion of tlie venae cavae and 25 minutes of the recovery 

 period. 



TABLE I 

 Vena Caval Occlusion in Differentially Cooled Dogs 



Lowest brain temperature 



Time 

 occluded 



15 min. 



15 min. 

 15 min. 

 20 min. 

 25 min. 

 25 min. 

 30 min. 

 30 min. 

 30 min. 

 35 min. 

 40 min. 



Result 

 Living and 

 Living and 

 Living and 

 Living and 

 Living and 

 Living and 

 Living and 

 Living and 

 Living and 

 Living and 

 Died in 24 



well 

 well 

 well 

 well 

 well 

 well 

 well 

 well 

 well 

 well 

 hrs. 



Certain of the animals seemed to tolerate this ordeal better than others but in each 

 case the heart continued to beat slowly and regularly during the interval of occki- 

 sion. Ten dogs shown in table I recovered without discernible damage. One dog, 

 cooled to a rectal temperature of only 31° C. and in A\hich the general circulation 

 was interrupted for more than 40 minutes did not regain consciousness and died 

 after 24 hours. This animal passed bloody mucus per rectum during the immediate 

 post-operative period. At autopsy the bowel was hemorrhagic and contained bloody 

 fluid. 



Three animals, shown in tal)lc' II. developed fatal cardiac arrhythmias as the 

 occluded venae cavae were being released. Two developed rapid fibrillation imme- 



