Principles of Separation

Abstract

SummaryExtracorporeal "blood purification," mainly in the form of hemodialysis has been a major portion of the clinical activity of many nephrologists for the past 5 decades. A possibly older procedure, therapeutic plasma exchange, separates and then removes plasma as a method of removing pathogenic material from the patient. In contrast to hemodialysis, therapeutic plasma exchange preferentially removes biologic substances of high molecular weight such as autoantibodies or alloantibodies, antigen-antibody complexes, and Ig paraproteins. These molecular targets may be cleared through two alternative procedures: centrifugal separation and membrane separation. This review presents operational features of each procedure, with relevance to the nephrologist. Kinetics of removal of these plasma constituents are based on the principles of separation by the apheresis technique and by features specific to each molecular target, including their production and compartmentalization in the body. Molecular targets for common renal conditions requiring therapeutic plasma exchange are also discussed in detail.

Prediction of immunoglobulin M reduction via therapeutic dose of simple plasma exchange and double filtration plasmapheresis using membrane separation in patients with hyperviscosity syndrome caused by Waldenstrom macroglobulinemia

“…However, the refilling effect would be trivial because the molecular weight of IgM is large (970 kDa) and 90% exists in intravascular space. 5,16,17 Results show that the amount of albumin administered as replacement fluid was significantly lower in DFPP than in PE, although IgM reduction rate levels in each session were not significantly different between DFPP and PE. The changes of serum albumin levels in each session were increased in PE, but remained unchanged in DFPP.…”

“…A second reason is production and refilling of monoclonal IgM during the interval among PE/DFPP. However, the refilling effect would be trivial because the molecular weight of IgM is large (970 kDa) and 90% exists in intravascular space …”

Membrane‐based therapeutic plasma exchange (mTPE): Technical and clinical experience

“…Separation of plasma from whole blood can be done using two different techniques, centrifuge and membrane. In centrifuge‐based therapeutic plasma exchange (cTPE) technology, the centripetal force from rotation of a blood chamber is used to separate cellular and acellular blood components based on differences in density . Although efficient in plasma removal, cTPE systems are often large and complicated and suffer from contamination of the separated plasma with platelets .…”

Is Plasma Exchange Efficacious in Shiga Toxin‐Associated Hemolytic Uremic Syndrome? A Narrative Review of Current Evidence

“…A one plasma volume exchange removes about 66% of an intravascular constituent and a two plasma volume exchange removes approximately 85% . Ideal characteristics of molecules to be removed are : an identified toxic or etiologic agent high molecular mass (≥15 000 D) slow rate of formation low turnover low volume of distribution …”