Fluid removal intensity in intermittent hemodialysis for acute kidney injury: net ultrafiltration rate characterization and outcomes

In patients receiving continuous renal replacement therapy (CRRT) for acute kidney injury (AKI), excessive net ultrafiltration (NUF) rates &gt;1.75 mL/kg/h have been associated with increased mortality, delayed AKI recovery and complications of hemodynamic instability. There is limited information on fluid removal practices and NUF rates in AKI patients treated with intermittent hemodialysis (IHD). We conducted a retrospective study of AKI patients who underwent IHD at our center between 2020 and 2023. The primary outcome was NUF rate, assessed as body weight-scaled, body surfaces area-scaled and unadjusted values. Secondary outcomes included mortality and measures of renal recovery at 90 days (estimated glomerular filtration rate [eGFR], major adverse kidney events [MAKE], IHD dependence and days to liberation from IHD). We studied 74 patients (median age 62 years [IQR 46–71], median baseline eGFR 81 mL/min/1.73 m² [IQR 71–96]). The median NUF rate was 5.61 mL/kg/h (weight scaled), 228 mL/h/m² (BSA-scaled), and 462 mL/h (unadjusted). Higher fluid removal rates were observed in patients with better baseline kidney function, while older age, diabetes and hypertension were associated with lower rates. No significant differences in AKI recovery, dialysis dependence, or change in renal function at 90 days were observed between high and low NUF groups. By 90 days, 45 patients (60.8%) had developed a MAKE. Among AKI patients, median NUF rates during IHD was higher than reported for CRRT and influenced by comorbidity and pre-morbid eGFR. At 90 days, MAKE was common, two thirds of patients had <i>a</i> &gt; 25% eGFR reduction, and one in 12 had died.