Net Fluid Balance Impacts Pediatric Continuous Renal Replacement Therapy Liberation

Objectives: The optimal fluid management strategy on continuous renal replacement therapy (CRRT) is unknown for critically ill children. The pace of ultrafiltration has been highlighted as a risk predictor for adverse outcomes in adult cohorts. Whether CRRT can cause dialytrauma through excessive ultrafiltration rates (UFRs) in children is undetermined. Although fluid overload (FO) at CRRT start has been associated with adverse outcomes, net fluid balance (NFB) on CRRT has not been investigated as a predictor for renal recovery. Design: Retrospective cohort study. Setting: Two quaternary PICUs. PATIENTS OR SUBJECTS: Children and young adults admitted between 2/2014 and 2/2020 at two quaternary pediatric hospitals who received CRRT. Interventions: None. Measurements and Main Results: Three hundred and seventy-one patients were included in this study with the median age of 85 months (interquartile range [IQR] 17-172), 180 (50%) were female. Three hundred and forty-five (96%) had acute kidney injury at CRRT start, 102 (28%) patients had FO > 15%. The median NFB on day 1 was 0.33 mL/kg/hr (-0.43 to 1.18), day 2 was -0.14 mL/kg/hr (-0.72 to 0.52), and day 3 was -0.24 mL/kg/hr (-0.85 to 0.42). Patients with a preserved urine output (UOP) greater than 0.3 mL/kg/hr over the study period had 5.6 more CRRT-free days and had decreased odds of major adverse kidney events at 30 days (MAKE-30). A NFB between -4.46 and -0.305 mL/kg/hr was independently associated with more CRRT-free days (β 2.90 [0.24-5.56]) and decreased odds of MAKE-30 (adjusted odds ratio 0.41 [0.22-0.79]). Conclusions: Ultrafiltration practices in children receiving CRRT are substantially different compared to adult cohorts. Patients with a more positive NFB had fewer CRRT-free days. Preservation of UOP was associated with more CRRT-free days. Whether UFR causes direct dialytrauma in critically ill children through impairment of organ perfusion and hemodynamics require further study to allow personalization of CRRT prescriptions to improve outcomes.