Given the shortages of banked blood, the risks of transfusion reactions, disease transmissions, and transfusion errors, we perfusionists must find ways to avoid blood transfusions. At the end of any given bypass run, there is residual blood left in the bypass circuit, the perfusionist must get this blood back to the patient. Most commonly either a cell saver or a hemoconcentrator (HC) has been used, in some fashion, to reinfuse residual circuit blood. The ideal method should: 1) be simple; 2) raise the hematocrit (HCT); 3) allow for changes in the patient's volume status; and 4) not compromise the integrity of the cardiopulmonary bypass (CPB) circuit allowing for rapid re-institution of CPB. We describe a technique in which residual CPB circuit blood is pumped through an HC directly to the patient via a 3/16-inch diameter line into a 16-gauge intravenous needle positioned in a peripheral or central vein. This allows the perfusionist to give back concentrated blood that is protein-rich while maintaining the above criteria.