Use of oXiris® vs standard AN69ST filters in sepsis-associated acute kidney injury requiring continuous renal replacement therapy: a retrospective matched cohort study

Background Sepsis-associated acute kidney injury (SA-AKI) is common in critically ill patients and carries high short-term mortality despite timely antimicrobials and organ support. Adsorptive hemofilters such as the oXiris ® membrane have been proposed as adjuncts during continuous renal replacement therapy (CRRT), but their patient-centered benefit remains uncertain. Methods We performed a retrospective matched cohort study within a dynamic cohort of consecutive adults with septic shock and SA-AKI requiring CRRT in a tertiary ICU in Medellín, Colombia (November 2020 - May 2023). Exposure was the hemofilter used at CRRT initiation (oXiris ® vs standard AN69ST). Patients were matched 2:1 without replacement using nearest-neighbor propensity scores based on age, Sequential Organ Failure Assessment (SOFA) score at ICU admission, time from ICU admission to CRRT initiation, and infection source. The primary outcome was 28-day all-cause mortality from ICU admission. Secondary outcomes included ventilator-free days and ICU–free days at day 28, CRRT duration, and ICU length of stay. Prespecified sensitivity analyses excluded COVID-19 cases and used inverse probability of treatment weighting (IPTW). Exploratory analyses assessed early changes in SOFA, lactate, PaO2/FiO2, mean arterial pressure, vasopressor dose, and C-reactive protein. Results After matching, 81 patients were included (53 standard filters and 28 oXiris ® ); 3 oXiris ® - patients were unmatched. Twenty-eight-day mortality was 69.8% (37/53) with standard filters and 67.9% (19/28) with oXiris ® . The adjusted risk ratio (RR) for oXiris ® was 0.95 (95% CI, 0.71-1.28; P = 0.76), with an absolute risk difference of -2.0% (95% CI, -23.2% to 19.3%). After excluding COVID-19 cases (n = 61), the adjusted RR was 1.05 (95% CI, 0.71-1.54; P = 0.81). IPTW analyses were directionally similar but considered secondary. Early physiologic changes showed no clear between-group differences. Conclusions In adults with septic shock and SA-AKI requiring CRRT, oXiris ® use was not associated with lower 28-day mortality compared with standard AN69ST filters. Secondary and exploratory finding should be interpreted cautiously given residual confounding and data limitations. Randomized trials with standardized protocols are needed to identify potential benefiting subgroups.