Plasmapheresis donors

Dolovich J, Sagona M, Pearson F, Buccholz D, Hiner E, Marshall C. Sensitization of repeat plasmapheresis donors to ethylene oxide gas. Transfusion 1987 27(l) 90-3. 

Plasma Collection. Human plasma is collected from donors either as a plasma donation, from which the red cells and other cellular components have been removed and returned to the donor by a process known as plasmapheresis, or in the form of a whole blood donation. These are referred to as source plasma and recovered plasma, respectively (Fig. 1). In both instances the donation is collected into a solution of anticoagulant (146) to prevent the donation from clotting and to maintain the stabiUty of the various constituents. Regulations in place to safeguard the donor specify both the frequency of donation and the volume that can be taken on each occasion (147). 

The need to transfuse blood components such as plasma, platelets, factor VIII, in addition to red blood cells (RBC) has generated the development of plasmapheresis (plasma separation from whole blood) and more generally that of apheresis (fractionation of blood components). Plasma collection from donors by centrifugation of blood bags began only in 1944. This technique was extended to therapeutic plasma purification in 1950, but RBCs were fragilized by the centrifugation and the plasma was not completely platelet-free. 

In contrast to hemodialysis that uses ultrafiltration membranes, plasma separation (also called plasmapheresis) requires microfiltration membranes with a pore size from 0.2 to 0.6 pm, in order to transmit all proteins and lipids, including LDL cholesterol (2000kDa) and retain completely platelets (2 pm diameter), red blood cells (8 pm diameter) and white blood cells. Thus, membrane plasmapheresis can yield high-quality platelet-free plasma and red cells can be either continuously returned to the donor or saved in another bag for blood transfusion. But it is important, in the case of plasma collection from donors, to minimize the membrane area, in order to reduce the cost of disposable hollow-fiber filters and to avoid the risk of hemolysis (free hemoglobin release) due to RBC damage by contact at the membrane if the pressure difference across the membrane is too high. 

Membrane plasmapheresis is also the first step for treatment of pathological plasma in the case of autoimmune diseases, as the patient retains his own red blood cells while his plasma is replaced by an albumin solution or fresh frozen plasma obtained from donors (plasma exchange therapy). Other more selective plasma purification techniques consist in eliminating pathologic immunoglobulins or LDL cholesterol familial hypercholesterolemia, either by a secondary filtration, chemical adsorption or immunoadsorption. A description of various applications of plasmapheresis can be found in the book edited by Smit Sibinga and Rater [15]. 

In France alone, about 220 000 plasmapheresis and 65 000 cytapheresis (collection of platelets, factor VIII, etc.) are performed every year, against 2 400000 blood donations. 600 ml of plasma can be collected from the same donor every 2 weeks if needed. 

Apheresis procedures are considered to be relatively safe when performed by experienced personnel. However, they are not without dangers, and there are some health risks to both patients and donors. Not unexpectedly, the risks are greater with therapeutic plasmapheresis on account of the underlying disease, with an estimated 3 deaths per 10 000 procedures (2). 

Plasmapheresis. The separation of plasma from whole blood by continuous membrane filtration represents an improvement over conventional centrifugation techniques in terms of efficiency, safety and cost. In the past, plasmapheresis was carried out with blood donors by collecting their whole blood in plastic bags which were then centrifuged to separate the red cells from the plasma. The supernatant plasma was then decanted and the red cells returned to the donorenabling plasma to be drawn from the same person as frequently as three times per week. Most of this plasma is then processed to yield purified components such as albumin or anti-hemophilic factor (Factor VIII). 

Continuous flow plasmapheresis is a superior alternative. Whole blood is continuously withdrawn from the donor and red cells are returned while plasma is continuously removed. There are two major advantages ... 

Plasmapheresis is the process in which plasma is separated from the cellular component of blood to allow separation of large molecular weight substances followed by replacement with donor plasma. This process can be performed with centrifugation or hemodialysis. 

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