Polytrauma survivors requiring kidney replacement therapy during the acute ICU phase: long-term clinical and kidney outcomes

Acute kidney injury (AKI) requiring continuous kidney replacement therapy (CKRT) is an uncommon but severe complication of polytrauma. Long-term kidney follow-up data in this population are scarce, particularly beyond the first years after injury. We evaluated survival, kidney outcomes, and predictors of adverse long-term trajectories in polytrauma survivors who required CKRT during the acute intensive care phase. This single-center observational cohort study included adult polytrauma patients admitted between January 2000 and December 2024 who survived the index hospitalization after AKI requiring CKRT. Of 68 hospital survivors, 62 were available for long-term follow-up. Patients were classified according to treatment timing as Early (< 72 h from admission; Early group n = 29) or Late (> 72 h; Late group n = 33). The primary endpoint of survival analysis was all-cause death, while in Cox analysis, age, Late/Early CKRT, pre-admission chronic kidney disease (CKD), and post-admission bladder dysfunction were explored as risk factors. Over 557.5 patient-years of cumulative follow-up (median 8.2 years), 45 of 62 patients (72.6%) were alive at the follow-up end. The clinical context was different in the groups: in the Late group, CKRT was strongly associated with septic shock-associated AKI (96.9% vs. 20.7%), whereas in the Early group with rhabdomyolysis (75.8% vs. 0.0%). Kaplan-Meier analysis showed better long-term survival in the Early group (p < 0.04). In Cox regression analysis, age showed a significant time-varying association with mortality, bladder dysfunction at discharge was also independently associated (adjusted HR 4.19, 95% CI 1.38–12.70; p = 0.011), and pre-admission CKD was borderline significantly associated with increased long-term mortality. Late versus Early CKRT was not independently associated with mortality after adjustment (adjusted HR 2.22, 95% CI 0.73–6.80; p = 0.163). Among long-term survivors, kidney function was generally stable, whereas the documented burden of comorbidities increased over time and was inversely correlated with eGFR. In most polytrauma survivors who required CKRT, durable kidney recovery was achievable even after very severe AKI. Long-term prognosis appeared to reflect age, baseline kidney vulnerability, post-traumatic functional sequelae, and the clinical trajectory leading to severe AKI, predominantly rhabdomyolysis-associated versus septic shock-associated AKI. This study reports very long-term nephrological follow-up in polytrauma survivors who required CKRT for severe AKI. Kidney function was generally preserved among long-term survivors despite severe AKI requiring CKRT. Early and Late CKRT identified different clinical trajectories, predominantly rhabdomyolysis-associated versus septic shock-associated AKI. Age and bladder dysfunction at discharge were associated with adverse long-term outcomes.