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These studies indicate that ultrapore filters in the venous and arterial lines of patients undergoing open-heart surgery will remove large quantities of potential embolic material from the bypass-patient circuit. A single venous line filter does not remove debris formed in the oxygenating system. The arterial line filters should be changed during pumping to permit maximum removal of debris.

A case is reported of excessive ultrafiltration and muscle cramps caused by fibrin partial occlusion of the coil venous outlet during multiple reuse. There was a normal pressure in the venous line. Th

Computer and mechanical models of the circulation have been made to study isotopic techniques of determining indices of myocardial blood flow. Parameters in the program and dimensions in the mechanical model have been scaled to represent the human circulation. Single rapid injections of 131I labelled human serum albumen were given into the venous line of the mechanical model and records obtained from collimated scintillation detectors positioned over the heart, lung and brain. Similar injections and recordings were simulated in the computer model. Two indices of myocardial flow have been studied. The first, described by Mena et al. is the ratio of the half time of the downslope of the left ventricular curve to the half time of the downslope of the brain curve. This index distinguished myocardial flows of 0,5% and 10% of total cardiac output but was also affected by changes in cerebral flow. A new index is proposed in which the half time of the left ventricular curve downslope is related to the half time of the downslope of the lung curve. This index can distinguish myocardial flows of 0,5% and 10% total flow but is not affected by changes in cerebral flow.

The generation of microaggregates during the extracorporeal circulation of heparinized blood through two types of hemodialyzers was demonstrated by increased screen filtration resistance. Arterial blood deoxygenation and widening of the alveolar-arterial oxygen difference occurred following either unfiltered or inadequately filtered dialysis. These changes were consistent with pulmonary microembolization. The blood gas abnormalities and the increased screen filtration resistance were reversed or improved when venous line microemboli filters were used.

Summary Disposable “Travenol” oxygenators are used for high flow perfusions using diluted blood with moderate hypothermia. A heat-exchanger is placed in the venous line from the patient. Blood is collected on the afternoon prior to surgery. Clinical and laboratory data from fifty patients are presented and discussed. This technique has proved to be simple, flexible and satisfactory.