Surface Area Effects on Efficiency and Biocompatibility in Experimental Membrane Plasmapheresis

The effect of different surface areas on cellular, humoral, and hemodynamic changes and on plasma separation performance were investigated. Membrane plasmapheresis, consisting of plasma separation and on-line reinfusion, was carried out on dogs for 3 h with 0.6 and 0.3-m2 polyethylene (PE) and polyvinyl alcohol (PVA) modules. The plasma separation and sieving performance was comparable in both the 0.6 and 0.3-m2 modules. The initial white blood count (WBC) reductions were independent of the surface area difference, but the rebound was greater in the smaller modules. The platelet (PLT) reductions were less with the 0.3-m2 PE module in comparison to those with the larger PE module, but no differences existed between both of the PVA modules. The smaller PVA module showed less complement activation compared to the 0.6-m2 module, whereas both of the PE modules showed comparable changes. Hemodynamic responses, especially the changes in pulmonary vascular resistance, were less with the smaller modules compared to the 0.6-m2 modules. The PE modules themselves showed less blood cellular, humoral, and hemodynamic changes compared to the PVA modules. The smaller modules showed greater rebound of WBC counts, however, PLT reductions, complement activation, and changes in hemodynamic parameters were less in the smaller modules.     

Ex Vivo Preclinical Evaluation of Membrane Plasma Separators

Four different types of hollow-fiber membrane plasma separators, constructed of cellulose acetate, polyvinyl alcohol, polyethylene, and polymethylmethacrylate membranes, were evaluated in ex vivo dog perfusions under conditions simulating their clinical use. An arteriovenous (A-V) fistula constructed in the dogs for blood access enabled repeated access to be achieved without surgical intervention. All modules produced transient leukopenia and a reduction of platelet counts. The polymethylmethacrylate module showed minimum reductions of white blood cell counts and CH50. The early leukocyte count reduction in membrane plasmapheresis is most likely related to the magnitude of complement activation by the membrane, as is seen with hemodialysis.     

Iliac artery-ureteral fistula developing after dilatation and stent placement

A fistula formed between the common iliac artery and the ureter following balloon dilatation of the distal ureter and stent placement in the presence of an ileal conduit. Possible causes are discussed.     

Summary of results of 1991 ASFA apheresis survey

As part of gathering data for its Networking Directory, the Registry/Directory Committee of the American Society for Apheresis solicited data on the types of apheresis procedures performed, equipment used, and diseases treated in the year 1991. In this voluntary solicitation of the 266 centers responding, 94% were from the United States. For those centers reporting exact numbers of procedures performed out of all institutions doing the procedures 48, 221 therapeutic and 330,702 donor procedures were reported. The dominant type of equipment being used is the centrifugal type. For therapeutic procedures plasma exchange is the most prevalent procedure and for donor procedures it is plateletpheresis. For therapeutics, Guillain-Barre syndrome was the most prevalent disease treated by plasmapheresis and leukemias by cytapheresis. The survey methodology proved to be valuable in gathering the data on a voluntary basis. With subsequent surveys and refinement of its methodology the apheresis practices in the United States could be assessed quantitatively to provide information on the number and types of procedures being carried out. Such information is required to assess the impact of apheresis technology on health care, to project trends, and to review the cost impact of this technology. © 1993 Wiley-Liss, Inc.     

Characterization of Polypropylene Membrane for Plasma Separation

Plasma separators of two different types constructed with polypropylene membrane were evaluated. Characterization of the membrane indicated that these separators meet the desired clinical requirements for sieving, filtration, and blood compatibility. In vitro sieving coefficients for albumin and total protein were 0.97 and 0.90, respectively. These modules showed a filtration flux dependency on blood shear rate. The ET filter (0.2 m2) had a higher shear rate for a given blood flow and also a higher flux. Based on the anticipated clinical applications at lower blood flows (less than 100 ml/min), small surface area devices having high shear rates meet clinical needs. The higher surface area module (Plasmaflux) also gave a satisfactory performance.