Addition of Hemofiltration to Expanded Hemodialysis Improves the Clearance of Large Middle Molecules Without Increasing Transmembrane Pressure or Reducing Serum Albumin

Background: Expanded hemodialysis (HDx) using the medium cut-off membrane Theranova improves clearance of middle and large middle molecules compared to conventional high-flux membranes. Although recent data suggest HDx is not inferior to online hemodiafiltration (HDF) in reducing mortality, convective hemofiltration may further enhance removal of uremic toxins. This study evaluated whether combining HDx with hemofiltration enhances solute removal without increasing TMP or albumin loss compared to HDx alone. Methods: 31 patients on maintenance HD underwent two consecutive dialysis sessions: one with HDx and one with HDxF (50 mL/min, nearly 12 L/session). To minimize sequence bias, we adopted a randomized cross-over design. Reduction ratios (RRs) of urea, creatinine, phosphate, β2-microglobulin (β2-MG), and lambda free light chain (λ-FLC) were calculated to assess solute removal efficiency. We measured the TMP at 60, 120, 180, and 240 minutes during the dialysis session and serum albumin levels before and after HD. Results: The mean age of patients was 49.9 ± 11.6 years, and 64.5% of participants were male (M:F=20:11). The mean dialysis duration was 9.5 ± 8.3 years. There were no significant differences in the RRs of urea, creatinine, phosphate, or β2-MG between HDx and HDxF. However, the RR of λ-FLC was significantly higher with HDxF than HDx only (38.6 ± 10.3% vs. 27.4±10.8%, p < 0.001). Serum albumin levels before and after dialysis were not significantly different in either the HDx group (3.4 ± 0.4 vs. 3.7 ± 0.6, p > 0.05) or the HDxF group (3.6 ± 0.5 vs. 3.7 ± 0.6, p > 0.05). Although TMPs under HDxF were significantly higher than those of HDx only at all measuring points (p < 0.001), they were maintained within the acceptable range of TMP. Conclusion: Compared to HDx alone, HDxF showed better removal of λ-FLC without significantly lowering serum albumin levels. Therefore, HDxF may be a better dialysis modality for reducing cardiovascular complications in HD patients.