ISCHEMIA AND C.N. S.— PONTIUS and DE BAKEY 



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Fig. 1. — Graph showing mortaHty for occlusion of descending thoracic aorta for one hour. 



difficult, owing to the fact that in the dog extensive collateral circulation exists in 

 the head and neck. Thus, occlusion of both carotid and vertebral arteries bilaterally 

 produced no apparent disturbances. A preparation was finally developed, however, 

 that resulted in a significant incidence of brain damage. This consisted in placing 

 a silver clip on the basilar artery through the foramen magnum, applying occluding 

 clamps to both carotid and vertebral arteries bilaterally and placing a tourniquet 

 aroiuid the neck to produce compression of the muscular collateral vessels. In the 

 control group of 9 dogs in which this was done for a period of 30 minutes, 6 (67 

 per cent) showed serious brain damage as manifested by convulsions, coma, and 

 death. Significantly, none of the 9 hypothermic dogs treated in like fashion devel- 

 oped any neurologic disturbances. These observations, therefore, suggest that hypo- 

 thermia is equally effective in preventing ischemic damage to the brain as to the 

 spinal cord following temporary arrest of the circulation to these highly vulnerable 

 tissues. 



These experimental observations on the protective value of hypothermia in pre- 

 venting ischemic damage to the central nervous system are supported by our 

 clinical experience with its use in the excisional therapy of aortic aneurysm. In 

 such cases in which the lesion is located in the thoracic aorta above the level of 

 the seventh dorsal vertebra the procedure of resection and graft replacement is 

 associated with the jeopardous effects of ischemic injury to the tissues of the 



