When is the optimal time to initiate renal-replacement therapy in the ICU? Patients with acute renal failure (a.k.a. acute kidney injury or AKI) in the ICU experience worse outcomes than patients who do not. As the kidneys shut down, toxic electrolytes and metabolic waste products build up in the blood. Intuition says -- screams, really -- that correcting the derangements with renal replacement therapy (hemodialysis or CRRT) must be helpful. But it's never been shown to what extent renal failure itself makes critical illness worse, or whether treating it (or when) helps. Some studies have suggested that rapid initiation of RRT in critical illness