Earlier identification of “silent” loss of filter performance and timely hemofilter replacement remain key challenges in CKRT. Many ICUs still replace filters only after overt clotting or circuit disconnection, increasing downtime and reducing the delivered dose, despite evidence of progressive declines in solute clearance and membrane performance. The FME multiFlux hemofilter series were developed to improve sustainability, reduce extracorporeal volume, and enhance permeability, particularly for middle molecular weight solutes. Building on data showing that reductions in effluent to serum ratios or small and middle molecule clearance can precede clinical signs of filter dysfunction, this study aims to demonstrate that multiFlux160 is non inferior to AV1000S, while characterizing longitudinal filter performance and defining practical clearance and pressure based trigger thresholds for proactive filter change.

This is a prospective, randomized, controlled, open label, multicenter, non inferiority trial comparing the efficacy and safety of the multiFlux160 hemofilter with the Ultraflux AV1000S in critically ill patients receiving CKRT in China. A total of 66 patients will be randomized 1:1 to multiFlux160 or AV1000S following informed consent. All patients will receive post dilution CVVHDF on multiFiltrate systems with blood flow 50–200 mL/min, adequate anticoagulation, and delivered dose 20–30 mL/kg/h. Filter performance will be assessed by serial FBR of small molecules (urea, creatinine) and middle molecules (β2 microglobulin, myoglobin, IL 6) at 2, 6, 12, 24, 48, and 72 hours after treatment initiation, simultaneous circuit pressure trends (TMP, PPRE, effluent, arterial, venous) will be recorded hourly. CKRT adequacy, safety, filter life, and predefined indications for ongoing treatment will be evaluated until CKRT discontinuation.

The study will report the primary FUN/BUN ratios non inferiority analysis, with detailed comparative profiles of small and middle molecule clearance, and a characterization of FBR and pressure trajectories preceding circuit failure, from which practical thresholds for earlier filter replacement will be proposed.

This study will provide the detailed characterization of solute-based and pressure‑based patterns of hemofilter performance loss. The findings are expected to inform practical, physiology‑based criteria for earlier filter replacement to reduce unplanned clotting, under‑delivery of prescribed dose and CKRT downtime.