270 PHYSIOLOGY OF INDUCED HYPOTHERMIA 



7. Gross, R. E., and Hufnagel, C. A. : Coarctation of the aorta : Experimental studies regarding 



its surgical correction, New Eng. J. Med. 223: 287, 1945. 



8. Parkins, W. M., Jensen, J. M., and Vars, H. M. : Brain cooling in the prevention of brain 



damage during periods of circulatory occlusion in dogs, Ann. Surg. 140: 284, 1954. 



9. Parkins, W. M., Ben, M., and Vars, H. M. : Tolerance of temporary occlusion of the thoracic 



aorta in normothermic and hypothermic dogs, Surgery 3S: 38, 1955. 



10. Pontius, R. G., Bloodwell, R. D., Cooley, D. A., and De Bakey, M. E. : The use of hypo- 



thermia in the prevention of brain damage following temporary arrest of the cerebral 

 circulation : Experimental observations. Surgical Forum, Clinical Congress of the American 

 College of Surgeons 5: 224-228, 1954. 



11. Pontius, R. G., Brockman, H. L., Hardy, F. G., Cooley, D. A., and De Bakey, M. E. : The 



use of hypotliermia in the prevention of paraplegia following temporary aortic occlusion : 

 Experimental observations. Surgery 36: iZ, 1954. 



12. Watkins, E., Jr. : Circulatory changes produced by clamping of the thoracic aorta. Surgery 



22: 530, 1947. 



DISCUSSION 



Dr. W. H. Lougheed: I was interested in this paper because in our series of 

 dogs, both the vertebral arteries and the common carotid arteries were occluded. 

 If all the vessels arising from both subclavians were ligated as well as the internal 

 mammary, then at normothermic temperatures these dogs showed cerebral damage. 

 However, if they were hypothermic, reduced to 2^ degrees Centigrade, we found 

 they were protected from 15 to 17 minutes. 



At 25° C. these animals had cerebral metabolic rates varying from 35 to 25% 

 of normal. This would indicate that they should withstand a period of anoxia 3 to 

 4 times longer than at normal body temperatiu'e. 



