The ability to store red blood cells (RBC) up to 42 days ensures a stable blood supply, and several randomized controlled trials have not found differences in mortality with older RBCs. However, storage lesions, a term used to describe the morphological and physiological alterations RBCs acquire during storage, are highly variable among donors and may be clinically significant. In order to gain a better understanding of the impact of storage lesions on the efficacy of transfusions, researchers used both murine models and ex vivo perfusion of human spleens to determine how rapidly storage-induced microerythrocytes (SMEs) (RBCs with a reduced size <43 µm2) were cleared from circulation. The percentage of SMEs in RBCs units varied widely between donors and increased from 5.2% (range 1.1% to 9.8% + 2.4% SD) on storage day 3 to 24.6% (range 4.9% to 68.1% + 13.6% SD) on day 42. Furthermore, units of RBCs with high proportions of SMEs correlated with poor transfusion recovery in autologous transfusions in volunteers (via 51Chr-labeling of RBCs). Using a novel ex vivo method with human spleens and murine models, the study team found that SMEs were rapidly sequestered by macrophages predominantly in the spleen. Further studies are needed to better understand donor variability with regard to storage lesions/RBC quality and transfusion recovery.
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What percent of morphologically normal RBC are left after the SMDs are cleared? If on day 30 more than 50% of RBCs have been rapidly removed from circulation? Can the rapid removal of the SME be saturated in a multiply transfused patient sho bas been transfused many units of red cells? It is fine to know the SMEs are rapidly cleared but what happens to tissue oxygenation, to damage on the endothelial cells caused by damaged red cells still pose challenges to transfusion medicine