Why is plasma exchange used in the treatment of rheumatic diseases?
Theoretically, PLEX should remove immune complexes and autoantibodies that contribute to the pathogenesis of some of the rheumatic diseases. It is most effective when used acutely to gain a rapid response in life-threatening situations. PLEX is usually used in combination with GCs and/or cytotoxic therapy to decrease the risk of a rebound flare of the underlying immunologic disease once the pheresis is stopped.
Most PLEX protocols remove 2 to 4 L (40 mL/kg = 1 plasma volume) of plasma over a 2-hour period daily. Each exchange of 1 to 1.5 plasma volumes removes 60% to 70% of plasma constituents. Replacement fluid is generally albumin-saline or another protein-containing solution. To decrease the risk of infection and bleeding, 1 to 2 units of fresh frozen plasma (FFP) are included as part of the replacement solution. If not, monitoring of fibrinogen, coagulation studies, and immunoglobulin levels are important. If the patient develops a low fibrinogen level (<200 mg/dL) or elevated international normalized ratio/partial thromboplastin time, then FFP is given. If patient develops hypogammaglobulinemia, IVIG (0.4 g/kg × 1 dose) is given. Cost of PLEX: >$5000 per session.