Time from acute kidney injury to continuous renal replacement therapy and outcomes in critically ill children.

Objectives: Literature in adults have demonstrated no differences in mortality based on the timing of renal replacement therapy (RRT) initiation. Pediatric studies have suggested that a longer duration between intensive care unit (ICU) admission and continuous RRT (CRRT) initiation is associated with worse outcomes. We aimed to investigate how the time between acute kidney injury (AKI) and CRRT initiation impacts outcomes in children, as this relationship remains uncertain. Methods: Retrospective cohort study of children (<18 years) admitted to the ICU who received CRRT between 2/2014 and 2/2020. Patients with chronic kidney disease, non-AKI, or fluid overload (FO) CRRT indications were excluded. The Pediatric Organ Dysfunction Information Update Mandate criteria were used to diagnose AKI. Exposures of interest were AKI onset (time between AKI and CRRT initiation) and AKI exposure (total number of days with each AKI criteria before CRRT). Our primary outcome was RRT-free days, censored at 30 days. Results: One hundred ninty-seven patients with a median age of 53.8 months (11.2-147.1) months received CRRT for a median of 13 (5-27) days. The median onset of AKI occurred 5 (2-7) days prior to CRRT start. For each additional day of AKI exposure before CRRT initiation there was a 0.42 decrease in RRT-free days. For every additional day between FO >15% and CRRT initiation the likelihood of dialysis liberation decreased [HR 0.82 (CI: 0.72-0.93)]. Conclusions: Earlier CRRT initiation after AKI onset was associated with more RRT-free days, while AKI, defined by FO >15%, was associated with dialysis dependence. Our findings suggest that delaying CRRT in critically ill pediatric patients may lead to worse outcomes.