Dialysis membranes high-flux

The seminal discovery that transformed membrane separation from a laboratory to an industrial process was the development, in the early 1960s, of the Loeb-Sourirajan process for making defect-free, high flux, asymmetric reverse osmosis membranes (5). These membranes consist of an ultrathin, selective surface film on a microporous support, which provides the mechanical strength. The flux of the first Loeb-Sourirajan reverse osmosis membrane was 10 times higher than that of any membrane then avaUable and made reverse osmosis practical. The work of Loeb and Sourirajan, and the timely infusion of large sums of research doUars from the U.S. Department of Interior, Office of Saline Water (OSW), resulted in the commercialization of reverse osmosis (qv) and was a primary factor in the development of ultrafiltration (qv) and microfiltration. The development of electro dialysis was also aided by OSW funding. 

Rousaud BE, Garcia JM, Camps EM, Cubells TD, Comamala MR. ACE inhibitors and anaphylactoid reactions to high-flux membrane dialysis (AN69) clinical aspects. Nephron 1992 60 487. 

Dialysis membranes are classified as conventional (standard), high-efficiency, and high-flux. Conventional dialyzers, mostly made of cuprophane, have small pores that limit clearance to relatively smaU molecules such as urea and creatinine. High-efficiency membranes have large surface areas and thus have a greater ability to remove water, urea, and other small molecules from the blood. High-flux... 

In the counter-current mode the magnitude of this difference is set by the construction of the dialyzer and the dialysate pressure control and is generally on the order of 50 mm Hg or greater. This minimum pressure will induce an absolute minimum ultrafiltration rate of 350 ml/hr for a typical high flux membrane. Thus, when the patient has lost sufficient water or perhaps when he does not need to lose any water during dialysis, the patient must continuously be given sterile saline to make up for the minimum ultrafiltration loses. 

The use of high-flux membranes gained significant support in 1985 when Geyjo et al. [343] conclusively estahfished the link between the accumulation of P2M and a compfication of long-term dialysis called dialysis-related amyloidosis (DRA). As kidney failure progresses, P2M concentration in the extracellular compartments increases, often to levels... 

Fresh high-flux dialysis membranes achieve approximately 23—37% reductions in plasma P2M levels [344]. However, dialyzer reuse significantly impairs the removal of P2M [345]. Indeed, it has been recognized that non-specific adsorption of middle molecules on the surface of these synthetic high-flux membranes, rather than difiusion through the membrane, can account for significant amounts of the device s clearance [346, 347]. With the surface area of membranes in the dialysis device amounting to less than 2 m, the adsorption capacity of the device is obviously too small. 

In order to obtain a high flux, the membranes should be as thin as possible. Figure VI -44 gives a schematic drawing of the dialysis process where feed stream and dialysate or permeate stream are flowing counier-currentiy (see also chapter Vni). 

DRA is the product of exposure to high concentrations of B2M, an 11.8-kDa major histocompatibility glycoprotein expressed on cell surfaces and normally cleared by the kidney— but not by low-flux HD membranes. Recent data demonstrates that B2M clearance by high-flux membrane dialysis exceeds that achieved by peritoneal dialysis, intimating that peritoneal dialysis may be associated with a similar incidence of DRA if employed long enough. 

Fig. 13.3 Worldwide changes of dialysis membrane properties observed between the years 2000 and 2013. Cellulose-based membranes have lost their importance and market share continuously. They are replaced by synthetic polymers as membrane materials. In addition flux has become an issue either. High-flux membranes, characterized by their ultraflltration coefficient to be UFC => 20 [ml/h-mmHg] are now used in more than two thirds of aU dialysis centers...

Verresen, L., Waer, M., Vanrenterghem, Y., MicMelsen, P. Angiotensin-converting-enzyme-inhibitors and anaphylactic reactions to high-flux membrane dialysis. Lancet 336,1360-1362 (1990)... 

LegaUais, C., Catapano, G., von Harten, B., and Baurmeister, U. (1998). Technique for the estimation of the diffusive permeability of high flux dialysis membranes. Int. J. Artif. Organs 21(10), 595. 

Ronco, C., and Bowry, S. (2001). Nanoscale modulation of the pore dimensions, size distribution and structure of a new polysulfone-based high-flux dialysis membrane. Int. J. Artif. Organs 24, 726. 

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