Relationship between packed cell volume, platelets, and platelet survival in red blood cell-hypertransfused mice

In this study we have measured platelet and megakaryocyte concentration, blood volume, and platelet survival of mice after RBC hypertransfusion to PCVs of 62% to 90%. The platelet concentration of mice with PCVs up to 75% was decreased by up to one half. At higher PCVs a more severe thrombocytopenia developed, with platelet concentrations decreased to less than 10% of baseline in approximately one half of the mice. Blood volumes of the hypertransfused mice were increased up to twofold. Megakaryocyte concentrations were normal or increased. Platelet survival in mice with PCVs less than 75% was normal but was sharply decreased for mice with higher PCVs. The decrease in platelet concentration at moderately elevated PCVs may be explained by hemodilution in the larger blood volume. However, hemodilution alone cannot explain the severe thrombocytopenia at higher PCVs. The presence of decreased platelet survival with normal or increased megakaryocyte concentrations in this latter group suggests that the severe thrombocytopenia is the result of more rapid platelet destruction. In summary, elevation of the PCV by RBC hypertransfusion produces thrombocytopenia. The severity of the thrombocytopenia and the mechanisms involved in producing it change abruptly when the PCV exceeds 75%. These findings should be considered in interpretations of the influence of RBC hypertransfusion on hematopoiesis and in clinical and experimental studies of thrombopoiesis in polycythemic subjects.