Membrane plasma exchange: principles and application techniques.

Membrane plasmapheresis was introduced in 1978 as a new method for performing therapeutic plasma exchange. Its principal advantages over traditional techniques include speed, ease of performance, and ready adaptability to clinical centers already performing routine extracorporeal therapy. The appearance of a membrane plasmapheresis circuit (vascular access, anticoagulation, connectology) is similar to that of hemodialysis and especially hemofiltration; the operating protocols (treatment time, filtration rates, pressures, pharmacokinetics) are quite different. Particular attention must be paid to avoiding operating conditions that lead to hemolysis. In clinical use membrane plasma separation is as effective as centrifugal plasma exchange in removing plasma proteins. The sieving coefficients for proteins with a molecular weight (MW) ranging from 67,000 (albumin) to 2,400,000 (beta-lipoprotein) daltons are unity. An exchange of one patient plasma volume has been shown to cause a 55% reduction of the serum levels of intravascular proteins. There are no significant differences between membrane and centrifugal plasmapheresis in substitution fluid requirements (human albumin or fresh frozen plasma), indications for treatment and complications. The next major advance in plasmapheresis technology will almost certainly be development of a "closed loop" circuit in which filtered plasma is treated to remove the offending moiety and returned to the patient. This would eliminate both the cost and the possible side effects of replacement fluid. Membrane-based systems are already available for removing cryoglobulins or proteins with MW of at least 900,000 daltons.