Apheresis literally means “to take away,” and blood apheresis procedures involve the selective removal of a targeted portion of blood, with return of the non-targeted portions to the individual. Such procedures may be done either to collect a blood product or treat a disease.
In blood donor centers, sophisticated apheresis machines remove whole blood from a donor, apply differential centrifugation to select a specific portion of the blood for harvest (e.g., platelets), and return the vast majority of the remainder of the blood to the donor. About 90% of the platelets transfused in the United States today are collected in this manner (“apheresis platelets,” or sometimes, “single-donor platelets”), and a growing proportion of red blood cells and plasma are collected using this technology.
Apheresis is also used to treat diseases (“therapeutic apheresis“). A few examples: To decrease the number of circulating white blood cells (leukemics in blast crisis), remove abnormal elements in plasma (hyperviscosity syndromes or thrombotic thrombocytopenic purpura), remove increased numbers of platelets (essential thrombocytosis), decrease hematocrit or iron load (polycythemia or hemochromatosis), or exchange abnormal red blood cells for normal ones (exchange transfusion in sickle cell disease). You can learn more about general principles of therapeutic apheresis in Blood Bank Guy Essentials Episode 025, more about using it to treat TTP in Episode 026, and much more about cytoreductions and red cell exchange in episode 049CE (with free CME and P.A.C.E. credits available for the last one!).
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