The purpose of the present study was to establish a continuous hemofiltration model using porcine blood to compare filter life. Continuous hemofiltration (CHF) experiments were performed using an in vitro hemofilter evaluation system utilizing porcine blood containing trisodium citrate in addition to nafamostat mesilate as anticoagulants. The lifetime of the hemofilter was evaluated using the transmembrane pressure and the pressure drop across the hemofilter at varying trisodium citrate concentrations. The porcine blood used in this experiment was considered to be in a slightly hypercoagulable state because of the continuous contact with non-biological materials and calcium inflow from substitution fluid. Blood containing 7 or 8 mM of trisodium citrate and nafamostat mesilate could be effectively used to compare the lifetimes of hemofilters utilized under the same conditions. In this CHF model using porcine blood, the plugging of the hollow fibers occurred shortly after the plugging of the membrane pores. In conclusion, a CHF model using porcine blood can be established by adjusting the concentration of trisodium citrate added to the blood.

Background and Aims Clotting within the membrane and/or venous ‘air trap’ chamber is common problems during continuous blood purification therapy. Frequent clotting during continuous blood purification therapy leads to inadequate solute removal, an increased circuit and filter cost, and an increased burden for the medical staff. Improvements in filter membrane materials may reduce the extent of clotting and prolong the filter life. The purpose of the present study was to clarify the characteristics of an NV polymer-embedded membrane (NV-PS) after long-term use, especially the adhesiveness of blood cells and changes in the solute removal performance. Methods Continuous hemofiltration (CHF) experiments using a permeate recycle mode were performed for 24 h using the same porcine whole blood divided into two portions to compare the NV-PS with a conventional polysulfone membrane (PS). The activated clotting time was adjusted to within a range of 300–400 s. The change in the dextran sieving coefficient (SC) of the membrane and the residual blood clots in the filters were evaluated after the completion of the CHF experiment. Results The increase in the transmembrane pressure and the pressure drop of the hemofilter were significantly smaller using the NV-PS than with the PS. For larger molecules (SC $$ \leqq $$ ≦ 0.4), the reduction in SC after blood contact was significantly smaller for the NV-PS. Fewer blood cells remained in the residual blood clots when the NV-PS was used. Conclusion NV-PS has the advantages of showing a lower degree of reduction of the solute removal performance and also a lower degree of clogging of the hollow fibers during prolonged circulation. These characteristics may be expected to be advantageous when this membrane is used for continuous blood purification therapy in acute-phase patients.

BACKGROUND AND AIMS When polymethyl methacrylate (PMMA) membranes are used in renal replacement therapy, inflammatory cytokines and other substances are removed by adsorption. However, these filters are also prone to clogging and the filter lifetimes are likely to be short. In the present study, we investigated the effects of the hollow fiber inner diameter and membrane area of PMMA membranes on the filter lifetime and protein removal performance using an in vitro continuous hemofiltration (CHF) experimental model with porcine blood. METHOD Three filters with different hollow fiber inner diameters and membrane areas were used: CH-1.0N (membrane area, 1.0 m2; hollow fiber inner diameter, 200 µm), CH-1.0W (prototype: 1.0 m2; 240 µm), and CH-1.8W (1.8 m2; 240 µm). Blood samples from one pig were divided into three portions, and in vitro CHF experiments for each filter were performed at QB = 100 mL/min and QS = QF = 10 mL/min. The pressure changes, total protein concentration in the blood, and total protein amount in the filtrate were measured during the experiments. From the results of the pressure changes, the time for the TMP to reach 200 mmHg (corresponding to the time when the membrane pores were clogged) and the time for the pressure drop through the filter to reach 200 mmHg (corresponding to the time when the hollow fibers were clogged) were calculated as the filter lifetime for comparative evaluation. RESULTS The time for the TMP to reach 200 mmHg was significantly longer with CH-1.8W than that with CH-1.0N or CH-1.0W (Friedman test, P < .05, n = 15). The time for the pressure drop through the filter to reach 200 mmHg was significantly longer with CH-1.8W than that with CH-1.0N or CH-1.0W (Friedman test, P < 0.05, n = 15). The results suggest that an increased membrane surface area is an essential factor for extending the filter lifetime. The total protein adsorption was significantly higher for the CH-1.0W and CH-1.8W filters than for the CH-1.0N filter (two-way ANOVA and post hoc Tukey test, P < 0.01, n = 15). Thus, the membranes with larger hollow fiber inner diameters (CH-1.8W and CH-1.0W) adsorbed more protein. CONCLUSION A larger membrane area contributes to a longer filter lifetime, whereas increase in the hollow fiber inner diameter does not. On the other hand, the protein removal performance, especially the adsorption performance, was higher for membranes with larger hollow fiber inner diameters.

Background and Aims Since hemofilters used for continuous renal replacement therapy (CRRT) come in prolonged contact with blood during treatment, clotting and cell adhesion induced by contact of blood with the membrane often occur, increasing the risk to the patient and burden on the staff. Suppressed platelet adhesion and better biocompatibility have been reported with the use of a dialysis membrane whose surface has been modified with an NV polymer in patients on maintenance hemodialysis. Therefore, it may be advantageous to use the NV membrane as a hemofilter for CRRT. In the present study, we evaluated the solute removal performance change and blood cell adhesion on the NV membrane after it comes in contact with blood, to clarify the characteristics of the NV membrane for long-time use. Methods A new polysulfone membrane containing the NV polymer (SNV) and a conventional polysulfone membrane (SHG) were used for the ex vivo blood filtration experiment. To compare the solute removal performance change and blood cell adhesion after blood comes in contact with the membranes, porcine blood collected from a single animal was divided into two portions, and a 24-hour of continuous hemofiltration (CHF) experiment was performed. The circulation conditions were as follows; blood flow rate, 100 mL/min; filtrate flow rate, 20 mL/min; heparin dose adjusted as appropriate to maintain the activated clotting time from 300 to 400 sec during the experiment. We evaluated the time-courses of the transmembrane pressure (TMP) and pressure drop at the hemofilter and the change in the sieving coefficients of dextran of different molecular weights (molecular weight cutoff curve) before and after the experiment, and blood cell adhesion. The amount of blood cell adhesion was evaluated based on the hemoglobin content and lactate dehydrogenase (LDH) activity in the eluate from the residual blood clots on the hemofilter 24 hours after the CHF experiment. Results The changes in the TMP and the pressure drop were significantly lower with the use of SNV as compared to SHG (n = 9, p < 0.01). From the molecular weight cutoff curves before and after the experiment, the molecular weights when the sieving coefficient was 0.1 to 0.4, which reflect the pore size of the pores through which relatively small molecules can pass, decreased to a lower extent after blood contact with SNV as compared to SHG (n = 3, SC = 0.1-0.3, p < 0.05; SC = 0.4, p < 0.01).The hemoglobin content and LDH activity in the blood clots adhering to the membrane after the experiment were significantly lower in SNV as compared to SHG (n = 9; Hb, p < 0.01; LDH, p < 0.05), indicating that blood cell adhesion on SNV was less pronounced than that on SHG. Conclusion SNV suppressed the increase in the TMP and also the pressure drop, allowed a high rate of solute removal performance to be maintained, and suppresses blood cell adhesion to a greater extent as compared to the conventional polysulfone membrane.

Background When polymethyl methacrylate (PMMA) membranes are used in continuous renal replacement therapy, especially in patients with high cytokine levels, inflammatory cytokines and other substances are removed by the adsorption effect. However, such filters are prone to clogging, and the filter lifetime can be short. This study investigated the effects of hollow fiber inner diameter and membrane area on filter lifetime and protein removal performance using an in vitro continuous hemofiltration (CHF) experimental model with porcine blood. Methods Three types of filters with different hollow fiber inner diameters and membrane areas were used: CH-1.0N (membrane material, PMMA; membrane area, 1.0 m2; hollow fiber inner diameter, 200 µm), CH-1.0W (prototype: PMMA; 1.0 m2; 240 µm), and CH-1.8W (PMMA; 1.8 m2; 240 µm). During the experiment, pressure changes, filter lifetime measured from pressure and protein removal performance were measured using an in vitro CHF experimental model with porcine blood. Results The filter lifetime of CH-1.8W was significantly longer than those of CH-1.0N and CH-1.0W. The total protein adsorption was significantly higher for the CH-1.0W and CH-1.8W filters than for the CH-1.0N filter. Conclusions A larger membrane area from 1.0 to 1.8 m2 contributed to a longer filter lifetime, while an increase in the hollow fiber inner diameter from 200 to 240 µm did not. On the other hand, the protein removal performance, especially the adsorption performance, was higher for membranes with a larger hollow fiber inner diameter from 200 to 240 µm.