274 PHYSIOLOGY OF INDUCED HYPOTHERMIA 



suffered motor ataxia and two were markedl}' confused. ^Iliese motor and sensory 

 difficulties seemed to rapidly improve over several days but residuum remained for 

 several months. 



Discussion. The possil)ilitv of protecting tissues by cold has initiated extensive 

 laboratory and clinical investigation. Consideral)le protection can be afforded the 

 central nervous system and the measure of this is being rapidly defined.^' -'• ■- ^' "' '' 

 These experiments indicate that brain temperatures of 20° C. with general body 

 temperatures of 30° C. will protect the dog against 30 minutes of complete occlu- 

 sion of the circulation. Others have subjected dogs to general body temperatures 

 lower than the brain temperatures recorded here without evidence of neurological 

 damage.' Under the conditions of these experiments, however, neurological damage 

 was encountered at very low brain teiuperatures. 



The dog can be cooled by the method described to a brain temperature of 20° C. 

 and a rectal temperature of 32° C. wathin 15 to 20 minutes. It is believed that 

 this method of cooling might better reveal the separate effects of cold upon the 

 organism. It is expected that in future experiments the catheters can be manipu- 

 lated into position without endangering the carotid artery. 



The cold heart is vulnerable to arrhythmias and the experience of many in 

 applying resuscitative measures has been disappointing.''- " This liability seems to be 

 compounded by operative manipulation and especially at lower temperatures. In 

 the selectively cooled animal with the heart relatively warmer we lielieve that these 

 difficulties may be significantly less. 



REFERENCES 



1. Beattie, E. J., Adovasio, D., Keshishian, J. M., and Blades, B.: Refrigeration in experimental 



surgery of the aorta, Surg., Gynec. & Obst., 96: 711, 1953. 



2. Pontius, R. G., Bloodwell, R. D., Cooley, D. A., and De Bakey, M. E. : Use of hypothermia 



in prevention of brain damage following temporary arrest of cerebral circulation, Surg. 

 Forum, Vol. V., p. 224, 1954. 



3. Parkins, W. M., Jensen, J. M., and Yars, H. M.: Brain cooling in the prevention of Ijrain 



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



4. Williams, J. R., Presti, M., Carroll, J., Clasen, R., Garvin, J., and Beattie, E. J.: The effect 



on the central nervous system of interrupted circulation during refrigeration anesthesia, 

 Surg. Forum, Vol. V., p. 719, 1954. 



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



use of hypothermia in the prevention of paraplegia following temporary aortic occlusion, 

 Surg., 36: 2,?>, 1954. 



6. Parkins, W. M., Ben, M., and Vars, H. M. : Tolerance of temixjrary occlusion of the thoracic 



aorta in normothermic and hypothermic dogs, Surg., 38: 38, 1955. 



7. Niazi, S. A., and Lewis, F. J.: Resumption of heartbeat in dogs after standstill at low tem- 



peratures, Surgical Forum, Vol. V., p. 113, 1954. 



8. Kirby, C. K., Jensen, J. M., and Johnson, J.: Defibrillation of the ventricles under hypo- 



thermic conditions, Arch. Surg., 68: 663, 1954. 



9. Swan, H., Virtue, R. W., Blount, S. G., and Kircher, L. T. : Hypothermia in surgery ; 



analysis of 100 clinical cases, Ann. Surg., 142: 382, 1955. 



DISCUSSION 



Dr. W . M. Parkins: Y)v. \'ars. Dr. Hen, and 1 have been interested in the rela- 

 tive role of the liver and the intestine in the pathogenesis of ischeiuic shock in- 

 duced by temporary occlusion of the thoracic aorta, and the inlluencc dt h\po- 

 thernn'a in extending the tolerance time to such vascular occlusion. 



