Assessment of prescribed vs. achieved fluid balance during continuous renal replacement therapy and mortality outcome.

Background: Fluid management during continuous renal replacement therapy (CRRT) requires accuracy in the prescription of desired patient fluid balance (FB_Goal) and precision in the attainable patient fluid balance (FB_Achieved). Herein, we examined the association of the gap between prescribed vs. achieved patient fluid balance during CRRT (%FB_Gap) with hospital mortality in critically ill patients. Methods: Cohort study of critically ill adults with acute kidney injury (AKI) requiring CRRT and a prescription of negative fluid balance (mean patient fluid balance goal of negative ≥0.5 liters per day). Fluid management parameters included: 1) NUF (net ultrafiltration rate); 2) FB_Goal; 3) FB_Achieved; and 4) FB_Gap (% gap of fluid balance achieved vs. goal), all adjusted by patient's weight (kg) and duration of CRRT (hours). Results: Data from 653 patients (median of 102.2 patient-hours of CRRT) were analyzed. Mean (SD) age was 56.7 (14.6) years and 61.9% were male. Hospital mortality rate was 64%. Despite FB_Goal was similar in patients who died vs. survived, survivors achieved greater negative fluid balance during CRRT than non-survivors: median FB_Achieved -0.25 [-0.52 to -0.05] vs. 0.06 [-0.26 to 0.62] ml/kg/h, p<0.001. Median NUF was lower in patients who died vs. survived: 1.06 [0.63–1.47] vs. 1.22 [0.82–1.69] ml/kg/h, p<0.001, and median %FB_Gap was higher in patients who died (112.8%, 61.5 to 165.7) vs. survived (64.2%, 30.5 to 91.8), p<0.001. In multivariable models, higher %FB_Gap was independently associated with increased risk of hospital mortality: aOR (95% CI) 1.01 (1.01–1.02), p<0.001. NUF was not associated with hospital mortality when adjusted by %FB_Gap and other clinical parameters: aOR 0.96 (0.72–1.28), p = 0.771. Conclusions: Higher %FB_Gap was independently associated with an increased risk of hospital mortality in critically ill adults with AKI on CRRT in whom clinicians prescribed negative fluid balance via CRRT. %FB_Gap represents a novel quality indicator of CRRT delivery that could assist with operationalizing fluid management interventions during CRRT. [ABSTRACT FROM AUTHOR]