Transfusion of fresh whole blood stored (4° C) for short period fails to improve platelet aggregation on extracellular matrix and clinical hemostasis after cardiopulmonary bypass

It has recently been shown that the hemostatic effect of 1 unit of fresh whole blood is equivalent to the effect of 8 to 10 platelet units. This study was designed to evaluate the effect of short periods of cold (4° C) storage on the hemostatic effect of fresh whole blood transfusion in 36 patients immediately after cardiopulmonary bypass. Twelve patients (group A) received unrefrigerated fresh whole blood, 12 (group B) received fresh whole blood after 5 hours' storage at 4° C, and 12 (group C) after 24 hours' storage at 4° C. For evaluation of platelet function, a method with an extracellular matrix and an electron microscope was used. The platelet function was graded from 1 to 4, with grade 4 being normal aggregation. Postoperatively, group A patients bled less than groups B and C (267 ± 42 versus 397 ± 72 and 601 ± 172 ml/24 hr, respectively, p < 0.001) and therefore received fewer blood units (1.4 ± 0.5 versus 2 ± 0.9 and 3 ± 1.4, respectively, p < 0.01). Five patients of group A (42%) reached grade A aggregation after transfusion of unstored fresh whole blood, compared with two (17%) of group B and none (0%) of group C (p < 0.01). Posttransfusion platelet cound and mean platelet volume were not significantly different in the three groups. We conclude that storage at 4° C, even for a short period of 5 hours, diminishes the hemostatic effect of fresh whole blood by decreasing platelet aggregability.