page_title: Retrograde autologous priming
section_title: Homologous blood transfusion
hierarchical_section_title: Retrograde autologous priming / Background / Homologous blood transfusion
caption_attribution_description: English: Bird hematocrits (blood spun down to separate red blood cells from plasma), Delaware
context_page_description: Retrograde autologous priming 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. The processing of RAP includes three main steps, and the entire procedure of RAP 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 available to provide some benefits to reducing the requirements for red blood cell transfusion. However, there are still some studies showing a failure of RAP to limit the hemodilution after the open heart operation.
context_section_description: There are two primary methods, homologous blood transfusion and autologous blood transfusion, to reduce the massive blood loss resulted from different surgeries. Homologous blood transfusion refers to using blood from other compatible donors to improve the oxygen-carrying capacity for blood by raising the number and concentration of blood red cells. Autologous transfusion uses patients' own blood which is stored previously. Compared to autologous blood transfusion, the homologous blood transfusion has more side effects, such as postoperative Infection, immunosuppression and viral transmission. These adverse effects facilitate the development of approaches to conserve the blood during cardiac surgery. These methods contain preoperative autologous blood donation (PABD), acute normovolemic hemodilution (ANH) and cell salvage. There are two main ways to salvage red blood cells. Cell processing and direct injection. Cell processors are red cell washing devices like the Cell Saver that collect anticoagulated shed or recovered blood, wash and separate the red blood cells (RBC) by centrifugation. Filtration devices like HemoClear microfilter, constitute the second major type of blood salvage in operating rooms. In general, ultrafiltration devices filter the patient's anticoagulated whole blood. Direct transfusion is a blood salvaging method associated with cardiopulmonary bypass (CPB) circuits or other extracorporeal circuits (ECC) that are used in surgery such as coronary artery bypass grafts (CABG), valve replacement, or surgical repair of the great vessels. Following bypass surgery, the ECC circuit contains a significant volume of diluted whole blood that can be harvested in transfer bags and re-infused into patients.
  Furthermore, the number of patients requiring red blood transfusions could be anticipated by observing a variety of variables before cardiac surgery. The red cell mass, as a critical factor, it matches the assumption that the blood transfusion is commonly demanded by patients who have a low red cell mass during CPB. At the same time, these patients are more likely to have low hematocrit values. Patients expect to reduce the blood product used during surgery because the red blood transfusion generally has a negative physiologic impact and highly related cost. Especially when CPB is applied in surgical operations, there will be a large number of blood transfusions required due to blood loss and hemodilution.
caption: Hematocrit
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