Retrograde autologous priming (RAP) is a means to effectively and safely restrict the hemodilution caused by the direct homologous blood transfusion and reduce the blood transfusion requirements during cardiac surgery. It is also generally considered a blood conservation method used in most patients during the cardiopulmonary bypass (CPB). The processing of RAP includes three main steps, and the entire procedure of RAP (about 1L CPB prime volume) could be completed within 5 to 8 minutes. This technique is proposed by Panico in 1960 for the first time and restated by Rosengart in 1998 to eliminate or reduce the risk of hemodilution during CPB. Moreover, to precisely determine the clinical efficacy of RAP, many related studies were conducted. Most results of researches indicate that RAP is a