Influence of storage on red blood cell rheological properties.

Background: It is known that the age of transfused blood is a risk factor for the development of multiple organ failure in surgical patients. However, the character of hemorrheological changes in stored blood as well as the time when they appear remains disputable. We assumed that blood storage was accompanied by a progressive decrease of RBC deformability and rheological disorders. The degree of rheological disturbances should be directly proportional to the number of RBC with altered geometry.

Materials And Methods: Nine packages of RBC kept in adenine saline solution were examined from the 5th to the 42nd day of storage. RBC deformability index (DI) was determined by micropore filtration technique. RBC shape was estimated by means of scanning electron microscopy. Blood clotting time was measured by Sonoclot coagulation analyzer.

Results: Significant alterations of RBC shape started at the second week of storage and progressed during the rest of the storage period. RBC shape changes were accompanied by progressive decrease in DI and increase in hemolysis and acidosis. The correlation index between the percentage of abnormally shaped RBC and DI was -0.81 (P = 0.0258). Blood clotting progressively decreased after 2 weeks of storage, probably due to the exhaustion of some procoagulant plasma factors.

Conclusions: Serious hemorrheological disorders, including the decrease in RBC deformability secondary to shape abnormalities, acidosis, and the decrease of blood clotting, start already at the second week of storage and progress up to the end of the storage period. Transfusion of packed RBC older than 7 days may contribute to hemorrheological disorders in critically ill patients.