The Rheologic Properties and Oxygen Transport Capacity of Red Blood Cells Processed by 3 Different Types of Cell Saving, and Its Effects on Microcirculatory Blood Flow and Tissue Oxygenation in Vivo

Cell savers are routinely used in our hospital during off-pump coronary artery bypass grafting (OPCABG) to retrieve and wash blood that is lost during the operation. This washed blood is retransfused to the patient in order to prevent allogeneic blood transfusion.

For cell savers 3 different operating principles exist. The most common type uses discontinuous blood processing with a spinning bowl that is intermittently filled with blood, processed and emptied. A second type uses a continuous blood processing principle with a rotational disk. A third one is intermediate using features of both the discontinuous bowl technology and the continuous rotational disc technology. In all types of autotransfusion systems the wound blood is washed, concentrated and stored in a blood conservation bag.

In several studies hemoglobin levels, leucocyte and platelet counts in the washed cell saver blood have been measured, indicating differences between types of cell saving. In other studies biochemical markers of inflammation in the washed cell saver blood have been measured, also indicating differences between types of cell saving. Recently, blood bank blood at the end of its shelf life was washed using similar devices as proposed in this study. The investigated devices removed substances from the blood differently. However, the rheologic properties of the red blood cells were not assessed.

Despite widespread clinical use of cell savers, little is therefore known about the rheologic properties and oxygen transport capacity of the washed red blood cells. As the process of washing of the blood cells occurs with high centrifugal loads, there is concern about the elasticity and deformability of the processed red blood cells. Ultrastructural changes in cell saver washed red blood cells have been demonstrated using scanning electron microscopy suggesting poor performance of these cells in the microcirculation. Using the continuous type of cell saver, we previously could demonstrate a reduction in deformability and 2,3-Diphosphoglycerate (DPG) levels of the processed blood cells. The implication is that microcirculatory blood flow may be obstructed by blockage of the small blood vessels and, as 2,3-DPG regulates oxygen transfer, tissue oxygenation may also be hampered. However, at the moment the effects of retransfusion of the washed cell saver blood on microcirculatory blood flow and tissue oxygenation in patients are unknown.

Thus, in this study the investigator want to determine in vitro the rheologic properties and oxygen transport capacity of the washed blood processed by one of 3 different types of cell saving (discontinuous, continuous and mixed) and to measure in vivo after retransfusion of this processed blood in the patient the effects on microcirculatory blood flow, tissue oxygenation and organ damage using organ specific biomarkers.