Association between Net Ultrafiltration Rate and Renal Recovery among Critically Ill Adults with Acute Kidney Injury Receiving Continuous Renal Replacement Therapy: An Observational Cohort Study

Abstract

Median age was 67.3 (interquartile range [IQR], 57-76.3) years, 64.4% were male, median Acute Physiology and Chronic Health Evaluation-III score was 100 (IQR, 84-118), and 634 (44.2%) died by day 90. Kidney recovery occurred in 755 patients (52.7%). Using tertiles of UFNET rates, 3 groups were defined: high, >1.75; middle, 1.01-1.75; and low, <1.01 mL/kg/h. Proportion of patients alive and independent of RRT among the groups were 47.8 versus 57.2 versus 53.0%; p = 0.01. Using competing risk regression, higher UFNET rate tertile compared with middle (cause-specific hazard ratio [csHR], 0.79, 95% CI, 0.66-0.95; subdistribution hazard ratio [sHR], 0.80, 95% CI, 0.67-0.97) and lower (csHR, 0.69, 95% CI, 0.56-0.85; sHR, 0.78, 95% CI 0.64-0.95) tertiles were associated with a longer time to independence from RRT. Every 1.0 mL/kg/h increase in rate was associated with a lower probability of kidney recovery (csHR, 0.81, 95% CI, 0.74-0.89; and sHR, 0.87, 95% CI, 0.80-0.95). Using the joint model, longitudinal increases in UFNET rates were also associated with a lower renal recovery (β = -0.29, p < 0.001). UFNET rates >1.75 mL/kg/h compared with rates 1.01-1.75 and <1.01 mL/kg/h were associated with a longer duration of dependence on RRT. Randomized clinical trials are required to confirm this UFNET rate-outcome relationship.