Sepsis is a leading cause of acute kidney injury (AKI) in critically ill patients, with sepsis-associated AKI accounting for approximately 50% of all AKI cases in the intensive care unit. The pathophysiology of septic AKI involves a complex interplay of inflammation, endothelial dysfunction, and microvascular injury, leading to impaired renal perfusion and tubular damage. Despite advances in critical care, septic AKI remains associated with high mortality rates and significant risk of progression to chronic kidney disease.

Continuous renal replacement therapy (CRRT) is the standard extracorporeal treatment for AKI in hemodynamically unstable patients. The Oxiris hemofilter (Baxter/Vantive) is a specialized AN69-based membrane with enhanced adsorptive capacity for cytokines and endotoxins due to a polyethyleneimine surface treatment and heparin grafting. While Oxiris has demonstrated the ability to reduce circulating inflammatory mediators in septic patients, its impact on endothelial cell dysfunction and subsequent renal recovery has not been systematically evaluated.

This is a single-center, prospective, open-label, exploratory randomized controlled trial comparing CRRT using the Oxiris filter versus CRRT using a standard filter in patients with sepsis-associated AKI at Samsung Medical Center, Seoul, Korea. A total of 30 patients (15 per group) will be enrolled and allocated using stratified randomization based on SOFA score, baseline renal function, and presence of septic shock.

Eligible participants are adult patients (aged 19 years or older) diagnosed with sepsis according to Sepsis-3 criteria who develop AKI (KDIGO stage 2 or higher) requiring CRRT initiation. Key exclusion criteria include end-stage kidney disease, expected survival of less than 24 hours, prior CRRT within 72 hours, and contraindications to heparin-based anticoagulation. CRRT will be maintained for a minimum of 72 hours, with Oxiris filters replaced every 24 hours per manufacturer guidelines.

The primary endpoints are changes in endothelial cell function assessed using induced pluripotent stem cell-derived endothelial cells (iPSC-ECs) treated with patient plasma collected at three time points: CRRT initiation (baseline), day 3, and CRRT discontinuation. Endothelial function will be evaluated by tube formation assay (total tube length, branch points, mesh area) and reactive oxygen species (ROS) production. This iPSC-EC-based model provides a reproducible and standardized platform to directly assess the biological effects of Oxiris on vascular endothelial integrity under conditions mimicking the pathophysiological environment of septic AKI.

Secondary endpoints include 90-day all-cause mortality, renal recovery (defined as dialysis independence at 90 days), changes in hemodynamic parameters (vasopressor requirements, mean arterial pressure), CRRT duration, and serial measurements of blood and urine biomarkers including NGAL, KIM-1, MCP-1, RANTES, and TGF-beta. These biomarkers reflect inflammatory burden, endothelial dysfunction, and renal tubular injury, providing a comprehensive assessment of the therapeutic effects of Oxiris beyond standard cytokine clearance.

As this is an exploratory study, all p-values will be interpreted descriptively and results will be used to generate hypotheses and inform the design of future confirmatory trials. The study aims to provide mechanistic insights into whether enhanced cytokine and endotoxin removal by Oxiris translates into measurable improvements in endothelial function and clinical renal outcomes.

Inclusion Criteria:

• Adult patients with AKI, aged ≥ 19 years old
• Relevant disease states: sepsis-associated AKI

Exclusion Criteria:

• Age > 85 years old
• Uncontrolled malignancy
• End-stage kidney disease
• End-stage hepatic failure requiring MARS or liver transplantation
• End-stage heart failure requiring extracorporeal membrane oxygenation (ECMO), left ventricular assist device (LVAD), intra-aortic balloon pump (IABP), or heart transplantation