ON cARDIOVASCULAR DISEASES The Use of Extracorporeal Circulation in Cardiac Surgery

Extracorporeal circulation is now a well-established method which per- mits the surgical correction of intracardiac defects. There are many different ways to establish cardiac bypass,'4 and certainly all presently existing technics will be greatly modified and simplified in the coming years. Yet all would agree that the use of this surgical tool has greatly advanced the surgery of heart disease and will continue to do so. With methods becoming better standardized and the basic technics more firmly grounded, attention should be directed more closely to the selection of patients for operation than it has been heretofore. The purpose of this paper is to detail our criteria for this selection, following a brief review of the method of extracorporeal circulation in use at our institution and a summary of our surgical experience. Method of Extracorporeal Circvlation We believe that there are certain basic requirements which must be fulfilled by a satisfactory apparatus for extracorporeal circulation. The blood should be completely oxygenated without the production of airembohsmO,�gen tension should range between 100 and 300 mm of merci.iry,and carbon dioxide tension between 30 and 40 mm. of mercury. Flows should approximate those in effect prior to perfusion, usually vary- ing between 2 and 2.4 liters per minute per sQuar&�meter. When flows of this amount are in effect, the venous saturation remains in the neighbor- hood of 70 per cent, the patient's venous pressure varies from 5 to 15 mm. of mercury, and the mean arterial pressure is maintained in the neighbor- hood of 70 mm. of mercury. Normal body temperature should be main- tained and total buffer base and pH should not change significantly. The volume of blood should remain stable, and the pumping apparatus must