(ă-fĕr′ē-sĭs)
[Pronunciation]
[Gr. aphairesis, separation]

Removal of unwanted or pathological components from a patient's blood by means of a continuous-flow separator; the process is similar to hemodialysis, as treated blood is returned to the patient.
The removal of cellular material is termed cytapheresis; leukapheresis describes the removal of leukocytes only. Plasmapheresis, also called plasma exchange, involves removal of noncellular materials. Therapeutic apheresis has been used to treat blood hyperviscosity, cold agglutinin hemolytic anemia, posttransfusion purpura, thrombotic thrombocytopenic purpura, myasthenia gravis, sickle cell anemia, Guillain-Barré syndrome, familial hypercholesterolemia, and certain drug overdoses.