Maximal flow rates and sieving coefficients in different plasmafilters: Effects of increased membrane surfaces and effective length under standardized in vitro conditions

Abstract

In Europe, capillary membrane filters are the favored method for plasmapheresis and detoxification systems including a plasma separation unit. Using capillary membrane filters clearance depends on the filtration rate and the sieving coefficient (Qs) for the plasma substrates. We investigated whether the increase of the effective membrane surface of plasmafilters enables higher clearance rates than a small plasmafilter. Heparinized porcine blood (5 I.U./l) of healthy pigs was used for an in vitro circuit. Filter types used were from GAMBRO: n = 5 PF1000N (effective membrane surface: 0.15 m(2)), n = 4 PF2000N (0.35) and from ASAHI: n = 4 PLASMAFLO OP-05W (L) (0.5). Spontaneous hemolysis was chosen to indicate the individual threshold limit for maximal flow rates. Sieving coefficient was determined for ten parameters at lowest and highest blood flow (Qb) and filtration rates (Qf). PF1000N enabled maximal flow rates as high as PF2000N and PLASMAFLO (Qb/Qf in ml/min: 200/40). Qs for most substrates were similar between the filter types and the flow rates. Compared to PLASMAFLO, the filter type with the largest membrane surface, the PF1000N provided significantly better Qs for triglycerides and albumin and a trend for a better elimination of cholesterol, GGT, and LDH. The sieving properties of the PF2000N ranged between PF1000N and PLASMAFLO. Under standardized in vitro conditions, the larger plasmafilters tested did not improve the overall performance of the plasmapheresis procedure. Thus, enlargement of the membrane surface such as provided by two commercially available and clinically well-established plasmafilters could not be proven to enable higher clearance rates.

Removal Characteristics of Immunoglobulin G Subclasses by Conventional Plasma Exchange and Selective Plasma Exchange

“…We have previously reported that the SC of each substance by SePE was as follows: TNF‐α, 0.99; Alb, 0.73; IgG, 0.50; coagulation factor XIII (FXIII), 0.17; and Fib, 0.0; respectively . The SCs of plasma proteins and Fib by PE were approximately 1.00 . Therefore, compared with PE, a larger amount of PV should be processed during SePE for improving the removal of IgG.…”

Thermography as potential real-time technique to assess changes in flow distribution in hemofiltration

“…This disparity is not surprising as it is well known that the experimental design for research on membranes and filters is quite often unrelated to the modes of operation that are encountered during clinical applications. 4,5,14 Therefore, it would be important to provide a single method that allows visualization of flow distribution under all study conditions from in vitro to clinical application. As shown here, thermography systems could meet this demand because of a filter perfusion-related development of surface temperature profiles.…”

“…Using a clinically proven apheresis unit (AK10, Gambro, Germany), a recirculating in vitro circuit was assembled (Figure 1a) according to the whole blood in vitro system described previously. [12][13][14][15] The specifications for the hemofilter (type: only for experimental use) were as follows -membrane: polyacrylonitrile, surface: 1.8 m 2 ; effective length 18 cm; housing material: acrylonitrile styrene copolymer and polycarbonate; Ca. Asahi.…”

“…10,11 This phenomenon and recent technical improvements in thermography led us to hypothesize that thermal conduction by renal replacement therapy circuit materials may be suitable to visualize and assess flow distributions inside hemofilters in real time. Thus, an exploratory study was conducted using both an in vitro circuit [12][13][14][15] for thermography and select CT measurements to compare the thermographic data with the contrast media-indicated flow distribution in a hemofilter.…”

First Level Prevention Instead of Third Level Intervention—Review of Research to Improve Biocompatibility and Performance of Capillary Membrane Apheresis in Critically Ill Patients

“…We found that an increased tendency of RBCs for aggregation promotes the stasis of blood and can lead to blocked fibers. As low blood flow velocities support cell aggregation and even sedimentation, we concluded that increases in the membrane surface area (which are usually achieved by a combination of increased number and length of the hollow fibers) may deteriorate the overall situation . Using our in vitro model, we compared three plasmafilters as this membrane process/filter type is most vulnerable for insufficient blood flow rates.…”