Red Blood Cell Exchange: When and Why?

Erythrocytapheresis, red blood cell (RBC) depletion, and RBC exchange transfusions are apheresis techniques used to rapidly lower the circulating red blood cell mass or to exchange the patient erythrocyte mass with donor red blood cells. Automated RBC exchange is performed using an apheresis device, while manual RBC exchange is based on sequential phlebotomies and isovolemic replacement. The main indication for RBC depletion in hematopoietic stem cell transplantation is the bone marrow processing in major ABO-incompatible transplants. These patients are particularly at risk for immediate posttransplant hemolysis due to preformed circulating isohemagglutinins that lyse the donor erythrocytes in the transplant. RBC depletion is an effective measure to avoid this complication. On the contrary, patients with minor ABO-incompatible HSCT are at risk for developing delayed hemolysis due to a passenger lymphocyte syndrome. Mature donor lymphocytes start to produce isohemagglutinins against recipient’s erythrocytes causing a hemolysis that typically starts 1–2 weeks after the transplant. Reduction of circulating patient’s erythrocytes using RBC exchange transfusions is a possible prophylactic intervention to reduce the risk of this potentially life-threatening hemolysis.