Plasmapheresis: A procedure designed to deplete the body of blood plasma (the liquid part of the blood) without depleting the body of its blood cells. Whole blood is removed from the body, the plasma is separated from the cells, the cells are suspended in saline, a plasma substitute or donor plasma), and the reconstituted solution may be returned to the patient. The procedure is used to remove excess antibodies from the blood in lupus, multiple sclerosis, multiple myeloma, etc. Plasmapheresis carries with it the same risks as any intravenous procedure. The risk of infection increases with the use of donor plasma, which may carry viral particles despite screening procedures. The procedure is done in a clinic or hospital.