Role of red blood cells in the anemia-associated bleeding under high shear conditions.

Background: Red blood cells (RBCs) contribute to hemostasis under blood-flow, and anemia might contribute to a hemorrhagic diathesis. The majority of current laboratory techniques to assess hemostasis do not consider the effects of RBCs. An assay to determine the role of RBCs in hemostasis could be beneficial for clinical management. Objectives: To investigate the influence of RBCs in hemostasis. Methods: Hemostasis was investigated using a novel microchip flow-chamber system (T-TAS (R)) in an anemic patient with von Willebrand disease. Subsequently, the effects of RBCs in total thrombus analysis system (T-TAS) were examined using reconstituted whole blood at various hematocrit levels. Results: In vivo: When the patient was anemic and demonstrated persisted hemorrhagic symptoms despite the maintained adequate von Willebrand factor ristocetin cofactor activity levels, thrombus formation determined by T-TAS was delayed. However, transfusions of RBCs resolved bleeding symptom and, accordingly, the thrombus formation in T-TAS improved. In vitro: Thrombus formation determined by T-TAS at 1000 s(-1) was dose-dependent on hematocrit (the time to reach 10 kPa (T-10): 10.0 0, 9.5 +/- 1.4, 6.7 +/- 2.4, 2.8 +/- 1.6 min at hematocrits of 0%, 12.5%, 25% and 50%, respectively). Markedly defective thrombus formation (T-10 >10 min) was confirmed at a hematocrit <25% at 2000 s(-1). Conclusion: Red blood cells play an essential role in hemostasis under high shear, and RBC transfusions could be effective for refractory bleeding in patients with anemia. T-TAS measurements appear to reflect the hemostatic consequences of diminished red cell numbers under blood-flow, and could provide a valuable means for monitoring patients.