THE USE OF HYPOTHERMIA IN CARDIAC SURGERY* 



HENRY SWAN 



Because hypothermia slows the metaboHc processes of the body, oxygen con- 

 sumption and circulatory energy are reduced. This modality, therefore, suggested 

 itself as being of potential value in the operative therapy of heart disease. Indeed, 

 the possibility of this technique as a method for open intra-cardiac operation under 

 direct vision during total circulatory occlusion was the stimulus which, for the past 

 three years, has directed our experimental and clinical attention toward attempting 

 to elucidate some of the alterations in physiology occurring in cooled and rewarmed 

 individuals, and toward the elaboration of intracardiac operative techniques which 

 could be safely performed by this method. 



This report is concerned with an analysis of 24 patients who underwent standard 

 closed cardiac operations, and 81 patients who underwent 84 open-heart operative 

 procedures during hypothermia. 



Preparation of patients for hypothermic anesthesia is essentially similar to any 

 anesthetic procedure. Morphine, Demerol, barbiturates, and scopolamine are given 

 for pre-medication. Induction is usually with ether. Two intravenous cannulae are 

 placed to assure that this route for fluids or blood will be available. Electrocardio- 

 graph needle electrodes are connected and a rectal thermocouple inserted. Through- 

 out the induction and cooling period a surgeon is available for immediate cardiac 

 resuscitation if need arises. This precaution was instrumental in saving at least two 

 patients who underwent circulatory arrest before thoracotomy had been performed. 



When the patient is in second plane, third stage anesthesia he is placed in a tub 

 of tepid water. The head and arms are held up out of the water. If shivering ensues, 

 d-tubocurarine is given. When vital signs are stable, ice cubes are added to the 

 water. Hyperventilation is deliberately performed throughout the anesthetic ex- 

 perience, except during circulatory occlusion. 



The patient is removed from the tub w^hen the rectal temperature has reached 

 a point which is about two-thirds the desired fall. This figure varies somewhat, but 

 the end temperature can be estimated in this fashion, usually, within a margin of 

 error of one or one and a half degrees centigrade. To cool an infant requires about 

 10-15 minutes in the tul), while an obese adult may need as long as an hour or an 

 hour and 15 minutes. 



When the patient is removed from the tul), he is thoroughly dried. The pelvic 

 area is wrapped with one-inch felt which is taped in place. A standard diathermy 

 coil is then accurately placed, taking care that the patient is supported so his weight 

 does not lie on the coils. The diathermy is used to counteract a tendency to over- 

 drift in cooling, and to warm the patient immediately following completion of the 

 cardiac procedure. Blood replacement is begun early and attempt is made to keep 

 pace with the rate of loss. Indeed, transfusion slightly in excess of loss is considered 

 desirable. 



About ()ne4ialf of the patients show am-icular fibrillation when rectal lemjieratures 



* This study was aided in part by a grant fruni the L'nitcd States Public Health Service 

 (H-1559C), and in part by a grant from tlie American Heart .Association. 



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