Higher blood flow rates in anticoagulation-free CRRT improve circuit survival and clinical outcome.

Objective: Anticoagulation-free continuous renal replacement therapy (CRRT) is an essential modality for managing patients with a high bleeding risk; however, it confronts significant challenges stemming from a shortened circuit lifespan. Blood flow rate (BFR) has been recognized as a pivotal non-pharmacological determinant influencing circuit longevity. This retrospective cohort study aimed to systematically evaluate whether elevating BFR to 250 ml/min could enhance CRRT circuit survival compared with the conventional 200 ml/min in anticoagulation-free settings. Methods: We conducted a retrospective analysis of patients receiving anticoagulation-free CRRT from seven intensive care units at West China Hospital of Sichuan University between September 2023 and June 2024. The primary outcome was circuit lifespan, defined as the duration from CRRT initiation to termination due to clotting or other causes. Protective and risk factors were assessed using univariate and multivariate Cox proportional hazards regression. Secondary outcomes included the proportion of circuits achieving predefined lifespans and patient clinical outcomes. Results: Among 128 patients using 241 CRRT circuits (median age: 57 years; 74.27% male), circuits were stratified by BFR: 200 ml/min (n = 132) and 250 ml/min (n = 109). Survival analysis demonstrated significantly improved 72-hour circuit survival in the 250 ml/min group for both overall circuits (HR: 0.475, 95% CI: 0.329-0.685, P < .001), clotted circuits (HR: 0.469, 95% CI: 0.321-0.685, P < .001), and each patient's first circuit (HR: 0.610, 95% CI: 0.373-0.998, P = .046), with results remaining statistically significant after confounder adjustment. The 250 ml/min group exhibited longer median circuit lifespans (overall: 33.5 vs. 13 hours; clotted: 31 vs. 15.5 hours; first circuit: 37 vs. 18 hours; all P < .05) and higher proportions of circuits achieving predefined lifespans (12 h: 85.32% vs. 65.91%; 24 h: 64.22% vs. 30.30%; 48 h: 33.94% vs. 9.09%; 72 h: 13.76% vs. 3.79%; all P < .05). Multivariate analysis identified use of ST150 filter, exposure to non-CRRT anticoagulation agents, and higher activated partial thromboplastin time as protective factors, whereas higher substitute fluid rate, hyperlipidemia, and hematocrit ≥0.30 were associated with reduced circuit survival. Clinically, the 250 ml/min group had lower in-hospital mortality (65.14% vs. 81.06%, P = .005). Mediation analysis revealed that higher BFR might prolong circuit lifespan by reducing transmembrane pressure (TMP) increase, which accounted for up to 60.32% of the protective effect. Conclusion: A BFR of 250 ml/min significantly improved circuit survival in anticoagulation-free CRRT compared to 200 ml/min, likely mediated by TMP reduction. Moreover, patients receiving 250 ml/min BFR exhibited lower in-hospital mortality. Our results support adopting a higher BFR to optimize CRRT efficacy in anticoagulation-free settings. Larger-scale prospective trials are needed to validate the findings.