Conventional apheresis therapies: a review.

This article reviews advances in the scientific basis and medical practice of plasmapheresis and cytapheresis therapies. Newly-characterized autoantibodies in neuromyelitis optica, Guillain-Barre variants, anti-neutrophil cytoplasmic antibody (ANCA) vasculitides, etc., exemplify the modern molecular biology which now provides a rigorous framework of understanding for the clinical practice of plasmapheresis. Clinical trials continue to clarify the appropriate use of therapeutic plasmapheresis (TPE) in these and other diseases. Centrifugal (cTPE) and membrane filtration (mTPE) types of plasmapheresis are compared, with details of the plasmapheresis prescription, anticoagulation choices, replacement fluids and other practical considerations. Plasma removal is more efficient with cTPE; mTPE systems have a lower plasma extraction ratio, and therefore require higher blood flow rates or longer procedure times. Autoantibodies and other pathogenic macromolecules targeted for removal by plasmapheresis can be depleted predictably when the plasma is discarded, as in conventional TPE. On-line plasma processing to regenerate the patient's own plasma avoids the need for replacement albumin solutions or plasma transfusion, but is inherently less efficient at removing the target molecule, so usually requires a longer procedure. Therapeutic white cell reduction (leukapheresis), platelet reduction (thrombocytapheresis) and red cell exchange (erythrocytapheresis) require centrifugal apheresis systems.