Ronco C, Orlandini G, Brendolan A, Lupi A, La Greca G
Department of Nephrology, St. Bortolo Hospital, Vicenza, Italy.
Kidney Int. 1998 Sep;54(3):979-85. doi: 10.1046/j.1523-1755.1998.00049.x.
Hemodialysis using high flux membranes today is a commonly used therapy. The primary advantage is the larger spectrum of molecules removed with these membranes, and the mechanism of removal is in part due to a phenomenon of filtration and backfiltration along the length of the hollow fibers. We hypothesized that increasing the filtration and backfiltration fluxes by modifying the structure of the dialyzer could enhance the convective transport of various solutes.
A modified high flux dialyzer was compared to the standard model in terms of pressure profiles, filtration-backfiltration rates and solute clearances. The modification consisted on the placement of a O-ring around the fiber bundle to create a resistance for the flow of the dialysis solution external to the fibers. The study on filtration fluxes was carried out using a scintigraphic method previously described, and solute clearances were studied during ultrafiltration-controlled hemodialysis sessions.
Utilizing a net filtration condition proximal to zero, the rates of proximal filtration and distal backfiltration in the experimental dialyzer were significantly enhanced in comparison with the standard dialyzer. The pressure drop in the dialysate compartment could be increased significantly, thus permitting an increase in the positive transmembrane pressure in the first half of the dialyzer and a parallel increase in the negative transmembrane pressure in the second half of the dialyzer. This resulted in a significant enhancement of the convective transport of middle-large solutes as demonstrated by the increase in vitamin B12 and inulin clearances.
This approach suggests that changes in design of the dialyzer may affect its performance. The use of internal filtration is suggested to improve convection and dialyzer efficiency for larger solutes without the requirement for high volumes of replacement fluid, as is the case for current hemodiafiltration techniques.
如今，使用高通量膜进行血液透析是一种常用的治疗方法。其主要优点是这些膜能清除的分子范围更广，清除机制部分归因于沿中空纤维长度方向的过滤和反过滤现象。我们推测，通过改变透析器结构来增加过滤和反过滤通量，可增强各种溶质的对流传输。
在压力分布、过滤 - 反过滤速率和溶质清除率方面，将一种改良的高通量透析器与标准型号进行比较。改良措施包括在纤维束周围放置一个O形环，以对纤维外部的透析液流动产生阻力。使用先前描述的闪烁扫描法进行过滤通量研究，并在超滤控制的血液透析过程中研究溶质清除率。
在接近零的净过滤条件下，与标准透析器相比，实验性透析器的近端过滤和远端反过滤速率显著提高。透析液腔室的压力降可显著增加，从而使透析器前半部分的正跨膜压力增加，后半部分的负跨膜压力相应增加。这导致中大分子溶质的对流传输显著增强，维生素B12和菊粉清除率的增加证明了这一点。
这种方法表明透析器设计的改变可能会影响其性能。建议采用内部过滤来提高对流和透析器对较大溶质的效率，而无需像当前血液透析滤过技术那样需要大量的置换液。
