HYPOTHERAriA AND CARDIAC SURGERY— SWAN 411 



various degrees of hypothermia were utilized, aud have classified these cases in 

 three different groups. 



The first group was called "The Controlled Temperature Grou[)." In cases from 

 this group, the temperature ranged from 34° C. to 30° C. The second group, in 

 which temperatures ranged from 30° to 25° C, was called "The Moderate Hypo- 

 thermia Group." The third group, which was lahelled the "Deep Hypothermia 

 Group," included those cases in which temperatures went below 25° C. 



Most of these cases did not involve an interruption of the blood flow through the 

 heart. Thev were, for the most part, closed cardiac procedures, and hyi)othermia was 

 utilized because of the severe nature or character of the disease process. 



We attempted to analyze these cases with regard to the ill effects of hypothermia 

 alone. This was exceedingly difficult to do, particularly with respect to the cases in 

 the deep hypothermia group, since many of these patients had conditions which 

 were essentially incompatible with life. 



Of the 10 cases in the deep hyi)othermia group, only three cases survived the 

 immediate postoperative period, and there was only one long-term survivor. 



There were two patients who exhibited severe postoperative bleeding which might 

 possibly have been correlated with the degree of hypothermia. One of these patients 

 was re-explored and found to have multiple areas of bleeding for which little could 

 be accomplished. The other patient was treated merely by repeated aspirations. 

 and subsequently survived the procedure. Similar problems have been encountered 

 in cases of this type without the use of hypothermia. 



Our only conclusion was that in this series of 100 cases there was no death 

 clearly attributable to the use of hypothermia alone ; nor were there any complica- 

 tions that might not have occurred had the hypothermia not been used. 



Dr. Jean Cahu: I think that in operations on the bloodless heart there is a problem 

 if the duration of the arrest of the circulation is over 20 minutes. We have two 

 possibilities : ( 1 ) to infuse oxygenated blood into the occluded aorta so as to prolong 

 the circulation into the coronary system; or (2) to be not inhil)ited by this problem 

 and to consider that it is possible to operate on the bloodless heart for a period of 

 25 minutes without any blood sup])ly into the coronary system. In fact, that is 

 possible ; but yesterday, when I told you that it was possible to arrest the blood 

 circulation for 25 minutes without any ventricular fil)rillation because of sino-atrial 

 blockade, I gave you only 50 per cent of the problem and of the solution. 



To resuscitate the heart after 25 minutes of arrest of the circulation, we nuist 

 inject into the right chamber before the release of the caval clamping a mixture of 

 A.T.P. and cytochrome-C. Under those conditions it is possible to re-establish the 

 normal beat of the heart after only 30 seconds to one minute of cardiac massage. 

 The cardiac massage must be done carefully. \\'e have only to push out of the 

 right cavity the blood and the mixture of A.T.P. and cytochrome-C. 



Lf. Col. Carl W . Hnghcs. MC. USA: In keeping with the constant concern with 

 ventricular fibrillation in the hypothermic animal, it was interesting to note in the 

 film by Drs. Andjus, Smith, and Lovelock that in the supercooled animal, con- 

 sideration was given to rewarming the heart faster than the rest of the body. At 

 the Walter Reed Armv Institute of Research, in a study of the tolerance of the 

 hypothermic normal dog's heart to ventricular fil)rillation, adult dogs were cooled 

 until spontaneous ventricular fibrillation occurred. The animals were allowed to 



