420 PHYSIOLOGY OF INDUCED HYPOTHERMIA 



the depth of tissues which must be transcended by the decreasing temperature wave 

 is less. Blood stream cooling is more uniform and drift is minimal. 



4. Prevention of shivering. Shivering should be prevented during the process. 

 When it occurs, cooling is more difficult. The oxygen consumption during shiver- 

 ing is greatly increased. It is especially important, therefore, to prevent shivering 

 in cyanotic patients where one desires to maintain as high an oxygen saturation in 

 the circulating blood as possible. When shivering occurs, it may be controlled by 

 administering small doses of the muscle relaxants and if the anesthesia is especially 

 light at this point, one may deepen it. 



5. Degree of ventilation. The majority of those questioned used hyperventilation 

 during hypothermia. Its use is based on the work of Swan and associates^ in order 

 to maintain a relatively constant pH during the cooling process. Lewis and asso- 

 ciates,^® however, use an artificial respirating system throughout in order to main- 

 tain a constant respiratory rate. CO 2 (5 per cent) is added to the respiratory mix- 

 ture to avoid the efifects of hyperventilation at low temperatures and prevent the 

 development of respiratory alkalosis. 



REFERENCES 



1. Swan, H., Zeavin, I., Holmes, J- H., and Montgomery, V. : Cessation of circulation in gen- 



eral hypothermia: I. Physiologic changes and their control, Ann. Surg. 128:ib0, 1953. 



2. Swan, H., Virtue, R. W., Blount, J. G., and Kircher, L. T. : Hypothermia in surgery : 



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



3. Bigelow, W. G., Callaghan, J. C, and Hopps, J. A. : General hypothermia for experimental 



intracardiac surgery, Ann. Surg. 132: 531, 1950. 



4. Hegnauer, A. H., D'Amato, H., and Flynn, J. : Influence of intraventricular catheters on 



course of immersion hypothermia in dog. Am. J. Physiol. 167 : 7i, 1951. 



5. Hegnauer, A. H., Shriber, W. J., and Haterius, H. O. : Cardiovascular response of the dog 



to immersion hypothermia, Am. J. Physiol. 161: 455, 1950. 



6. Bigelow, W. G., Lindsay, W. K. and Greenwood, W. F. : Hypothermia. Its possible role in 



cardiac surgery : An investigation of factors governing survival in dogs at low body tem- 

 peratures, Ann. Surg. 132: 849, 1950. 



7. Shumacker, H. B. : Personal communication, July 1955. 



8. Kaplan, S. : Discussion of paper "Cardiac surgery under hypothermia" by C. P. Bailey, cf ah. 



Jour. Thoracic Surg. 27: 92, 1954. 



9. Collins, H. A., Stahlman, M., and Scott, H. W., Jr. : The occurrence of subcutaneous fat 



necrosis in an infant following induced hypothermia used as an adjuvant in cardiac sur- 

 gery, Ann. Surg. 138: 880, 1953. 



10. Langer : Quoted by Lemez, L. : Beitrag zur Pathogenese der subcutanen Fettgewebsnekrose 



Neugeborener (sog. Sclerodermia neonatorum) an der Hand einer Kiiltereaktion des sub- 

 cutanen Fettgewebes bei neugeborenen und jungen Siiuglingen, Ztschr. f. Kinderh. 46: Z22), 

 1928. 



11. Cookson, B. A., Neptune, W. B., and Bailey, C. P.: Hypothermia as a means of performing 



intracardiac surgery under direct vision, Dis. Chest, 22:245, 1952. 



12. Adams-Ray, J. : Serafimerlasseretet, Stockholm. Personal communication, September 1955. 



13. Pierpont, H. C, and Blades, B. : A simple method for inducing hvpothermia, Ann. Surg. 



140: 4, 1954. 



14. Shumacker, H. B.: Panel discussion on advantages and disadvantages of various methods 



in hypothermia. International Symposium, Cardiovascular Surgery, Henry Ford Hospital, 

 1955. 



