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 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.

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.