Protocol for the OxiCLEAR Study: In Vivo Saturation and Adsorption Kinetics of the Oxiris Hemofilter in Septic Shock.

INTRODUCTION: Extracorporeal blood purification is increasingly used as adjunctive therapy in septic shock to modulate dysregulated host immune responses. The AN69-polyethyleneimine-based Oxiris hemofilter combines renal replacement therapy with non-selective adsorption of endotoxin and inflammatory mediators. Despite its widespread clinical use and reported biological and hemodynamic effects, the in vivo adsorption capacity, saturation kinetics, and duration of effective solute removal during routine clinical application remain insufficiently characterized. METHODS: This is a prospective, single-center observational cohort study enrolling 29 adult patients with septic shock and sepsis-associated acute kidney injury undergoing continuous veno-venous hemofiltration with the Oxiris hemofilter as part of standard care. Both blood samples (from the inlet and outlet of the extracorporeal circuit) and effluent samples will be collected at predefined time points within the first 24 hours of treatment. Endotoxin concentrations will be measured using a high-sensitivity competitive enzyme-linked immunosorbent assay, and inflammatory mediators will be quantified using multiplex immunoassays. The primary analysis will evaluate the dynamic adsorption capacity and saturation behavior of the Oxiris membrane for endotoxin and inflammatory mediators by analyzing the relationship between inlet concentrations and adsorption rates over time using Pearson correlation coefficients with Fisher's Z transformation. Secondary outcomes include changes in hemodynamics, lactate, inflammatory biomarkers, renal recovery, intensive care unit length of stay, and 28-day mortality. CONCLUSION: This study aims to provide systematic in vivo characterization of adsorption kinetics, clearance mechanisms, and saturation dynamics of the Oxiris hemofilter in septic shock. The findings are expected to support more rational filter replacement strategies and individualized treatment timing, thereby enabling a more targeted and evidence-based application of Oxiris therapy in critically ill patients. TRIAL REGISTRATION: ClinicalTrials.gov (registration number NCT07419802).