The red blood cell: An underestimated actor in alterations of the microcirculation*:

Utilization and quality of cryopreserved red blood cells in transfusion medicine

Cryopreserved (frozen) red blood cells have been used in transfusion medicine since the Vietnam war. The main method to freeze the red blood cells is by usage of glycerol. Although the usage of cryopreserved red blood cells was promising due to the prolonged storage time and the limited cellular deterioration at subzero temperatures, its usage have been hampered due to the more complex and labour intensive procedure and the limited shelf life of thawed products. Since the FDA approval of a closed (de) glycerolization procedure in 2002, allowing a prolonged postthaw storage of red blood cells up to 21 days at 2-6°C, cryopreserved red blood cells have become a more utilized blood product. Currently, cryopreserved red blood cells are mainly used in military operations and to stock red blood cells with rare phenotypes. Yet, cryopreserved red blood cells could also be useful to replenish temporary blood shortages, to prolong storage time before autologous transfusion and for IgA-deficient patients. This review describes the main methods to cryopreserve red blood cells, explores the quality of this blood product and highlights clinical settings in which cryopreserved red blood cells are or could be utilized.

The optimal hematocrit

Nearly 15 million units of packed red blood cells and whole blood are transfused annually in the United States alone. Until recently, the major risks from blood transfusion were thought to be transmission of viral infections, and overall, blood transfusion was believed by most providers to be safe. A safe hemoglobin threshold above which red cell transfusion is clearly unnecessary has not been established. This article addresses the numerous problems that surround the use and consequences of blood transfusion, such as hemoglobin and hematocrit levels, oxygenation, storage time, immunomodulation, infection, and anemia. The relevant literature is comprehensively reviewed.