EXCHANGE TRANSFUSION THERAPY AND ITS EFFECTS ON REAL-TIME MICROCIRCULATION IN PEDIATRIC SICKLE CELL ANEMIA PATIENTS: AN INTRAVITAL MICROSCOPY STUDY

Periodic blood exchange transfusion is a treatment modality commonly used to manage pediatric sickle cell anemia (SCA) at the University of California Davis Medical Center. The goal of exchange transfusion therapy is to ameliorate vasoocclusion and improve tissue perfusion by removing sickled red blood cells (RBCs) and introducing normal RBCs. Using computer-assisted intravital microscopy, pre- and post-transfusion microvascular characteristics were analyzed. In this study, the bulbar conjunctiva exhibited a “blanched” avascular appearance in all six pediatric SCA patients prior to transfusion, indicative of tissue hypoperfusion and ischemia. Immediately following transfusion, substantial improvement in vascularization and tissue perfusion resulted, reflected by the enhanced appearance of capillaries and arterioles. In addition, a decrease in red cell velocity was observed. These observations provide evidence that exchange transfusion therapy is beneficial in ameliorating vasoocclusion and improving tissue perfusion. However, with the paradoxical post-transfusion decrease in red cell velocity presumably due to induced hyperviscosity from the large transfusion volume, blood flow is still impaired. This decreased velocity may thwart efforts to improve oxygen delivery via transfusion and may, to some extent, promote vasoocclusion instead. This paradoxical result warrants further investigation on the effects of transfusion volume and viscosity in the exchange transfusion process.