Blood products are a limited resource and cardiac surgery is a high consumer. Processing residual cardiopulmonary bypass (CPB) volume via ultrafiltration may improve hemostasis and reduce transfusion through clearing activated complement, activated coagulation components, and proinflammatory cytokines. Unlike cell saver technology, ultrafiltration has the advantage of maintaining plasma proteins, platelets, and coagulation factors. We sought to establish if the processing of residual CPB volume with ultrafiltration reduces homologous blood transfusion and bleeding.