HYPOTPIERMIA AND CARDIAC SURGERY— SWAN 409 



Summary. ]. Kxperieiicc with 105 ])alicnts undergoing cardiac surgery during 

 hypothermia has been described and discussed. ( )\ these, Si had direct-vision open- 

 heart operations during circulatorv arrest. 



2. As currently ai)plie(l in our liands, tlie safe parameters for open-heart opera- 

 tions appear to be a right heart cardiotomy, hypothermia not deeper than 26° C, 

 and circulatory occlusion not to exceed eight minutes. 



3. The chief causes of death have been ventricular fil)rillation. post-operative 

 hemorrhage, and delayed thrombo-embolic phenomenon. The methods currently 

 being adopted to overcome these difficulties are discussed. 



4. For cyanotic patients and those with severe tachycardia, cooling appears to 

 improve operative risk when standard closed operations are performed. 



5. Pulmonary valvular and infundibular stenosis, and atrial septal defect, espe- 

 cially of the secundum variety, are efifectively treated at low risk by direct-vision 

 repair. At the present time, we consider this method the treatment of choice for 

 these lesions. 



DISCUSSION 



Dr. F. J. Leuns: Those of us who use hypothermia in Minnesota have used a 

 slightly different technique. Although we strive to avoid respiratory alkalosis and Dr. 

 Swan to produce it, there is some similarity, of course, because we both attempt to 

 maintain a constant pH level. That may be more important than anything else in 

 the technique. Except for that difference, most of our experience has agreed with 

 Dr. Swan's, and I think that hypothermia provides, mechanically, the simplest 

 method at the present time for doing open heart surgery. It provides the driest 

 operative field for this type of operation, and it provides the best way at the present 

 time, certainly, for doing open operations on adults where with heart-lung machines 

 and other techniques the problem is quite a bit more complicated than it is in in- 

 fants. In our own series of cases we have operated with success on adult patients 

 as old as 61. 



As to what operations you can do with hypothermia, I think that problem is 

 obviously still unsettled. With a careful exploration of the heart with the finger be- 

 fore the open cardiotomy, and a carefully rehearsed technique, a great deal can 

 be accomplished in seven minutes or less. For example, we recently operated on a 

 patient with total anomalous pulmonary venous drainage ; all the pulmonary veins 

 ended in the right atrium. To repair this we made a large atrial septal defect and 

 reconstructed the right atrium. The operation took eight minutes. Apparently the 

 results have been completely successful. Further examples can be given. Recently 

 we also operated on a tri-atrial heart under direct vision during hypothermia, and 

 that operation took but three and one-half minutes. Our average time for the atrial 

 septal defects has been four and one-half minutes. The high defects have taken us 

 the longest to repair. 



Dr. Jerome H. Kay: In order to prolong the time during which we can work 

 inside the right ventricle, Doctors Robert Gaertner, James Isaacs, Richard Dever, 

 and I have perfused the head and heart in a group of 157 animals. 



In all of these animals the right ventricle was open for 15 to 30 minutes. We 

 collected arterial blood from the femoral artery of donors and added 40 milligrams 



