Individuals with greater fluid overload at randomization may benefit more from the early beginning of renal replacement therapy (RRT) among critically ill patients with acute kidney injury (AKI). The Standard vs. Accelerated Initiation of Renal Replacement Therapy in Acute Kidney Injury (STARRT-AKI) experiment was analyzed using a predefined post hoc analysis. After adjusting for censoring due to death or ICU discharge, researchers used mixed models to assess the impact of early RRT on cumulative fluid balance over 14 days after randomization. They analyzed how fluid status at admission affects the results of RRT and other important clinical measures. To evaluate the impact of accelerated versus standard RRT initiation on clinical outcomes, patients’ quartile, risk ratios (95% CI) for categorical variables, and mean differences (95% CI) for continuous variables were calculated.

A total of 2,738 of the 2,927 patients included in the modified intention-to-treat analysis had baseline fluid balance data, and 2,716 (92.8% of the total) had fluid balance data for at least 1 day after randomization. Participants assigned to the accelerated method lost less fluid overall than those assigned to the control group over the next 2 weeks (4,509 (-728 to 11,698) mL versus 5,646 (0 to 13,151) mL, P=0.03). There was no significant improvement in 90-day survival associated with accelerated RRT initiation across any of the 4 quartiles of baseline fluid balance (quartile 1: RR 1.11 (95% CI 0.92 to 1.34), quartile 2: RR 1.03 (0.87 to 1.21); quartile 3: RR 1.08 (95% CI 0.91 to 1.27) and quartile 4: RR 0.87 (95% CI 0.73 to 1.03), P value for trend 0.08).

In critically ill patients with AKI, starting RRT sooner resulted in a moderate reduction in the overall fluid balance. However, expedited RRT initiation did not affect all-cause mortality among individuals with greater fluid accumulation at randomization.