Prognostic implications of the duration of continuous kidney replacement therapy in 3-month survivors of acute kidney injury: findings from the LINKA cohort

The duration of continuous kidney replacement therapy (CKRT) represents a complex clinical surrogate reflecting the severity of systemic illness, the rate of metabolic recovery, and clinical decision-making regarding treatment discontinuation. The effect of CKRT duration on long-term outcomes in patients with acute kidney injury (AKI) is unclear. This study aimed to identify factors associated with CKRT duration and evaluate its association with long-term renal outcomes and mortality. This multicenter, retrospective study included 1,436 patients with AKI who received CKRT between 2017 and 2022 and survived ≥ 3 months post-initiation. Participants were stratified into groups based on the median CKRT duration: short (≤ 4 days) or long duration (> 4 days). Multivariable logistic regression examined the factors associated with CKRT duration. Multivariable Cox proportional hazards regression evaluated the effect of CKRT duration on the risk of end-stage kidney disease (ESKD) and all-cause mortality. The incremental predictive value of CKRT duration beyond traditional clinical variables and the Sequential Organ Failure Assessment (SOFA) score was evaluated using differences in Harrell’s concordance index (ΔC-index), net reclassification improvement (NRI), and integrated discrimination improvement (IDI). The use of mechanical ventilation (adjusted odds ratio [aOR], 2.742; 95% confidence interval [CI], 1.990 − 3.792; P < 0.001), extracorporeal membrane oxygenation (aOR, 1.983; 95% CI, 1.223 − 3.267; P = 0.006), and higher C-reactive protein levels (aOR, 1.002; 95% CI, 1.001–1.004; P = 0.009) were significant predictors of long-duration CKRT. However, higher baseline urine output (aOR, 0.998; 95% CI, 0.996–1.000; P = 0.017) and platelet counts (aOR, 0.998; 95% CI, 0.996–0.999; P = 0.009) were independently associated with short-duration CKRT. During a mean follow-up of 17.8 months and 24.6 months, 26.1% of participants progressed to ESKD and 26.6% died, respectively. After adjusting for confounders, long-duration CKRT was independently associated with a significantly higher risk of ESKD (adjusted hazard ratio [aHR], 1.598; 95% CI, 1.260–2.025; P < 0.001) and all-cause mortality (aHR, 1.631; 95% CI, 1.310–2.032; P < 0.001). Addition of CKRT duration to baseline risk models including the SOFA score significantly enhanced risk reclassification and discrimination performance for both ESKD (ΔC-index = + 0.020, P < 0.001; NRI = 30.0%, P < 0.001; IDI = 0.024, P < 0.001) and all-cause mortality (ΔC-index = + 0.037, P < 0.001; NRI = 33.0%, P < 0.001; IDI = 0.033, P = 0.030). Prolonged CKRT was independently associated with an increased risk of long-term ESKD progression and all-cause mortality among 3-month survivors of AKI. Thus, the duration of CKRT may serve as a meaningful prognostic marker to identify high-risk patients who might benefit from close follow-up and tailored multidisciplinary management.