Early or delayed initiation of renal replacement therapy for critically ill patients—do we know the right time?

Acute kidney injury (AKI) is a common clinical condition among critically ill patients, especially complicated with sepsis or cardiothoracic surgery. Its incidence has been globally reported to reach 30–50% in intensive care units (ICUs) (1,2). Several internationally standardized diagnostic criteria of AKI have been suggested (3,4) and the latest AKI classification criteria was published by Kidney Disease Improving Global Outcomes (KDIGO) in 2012 with the stratification of AKI patients by serum creatinine level and urine output (5). Although ideal management of AKI patients in ICU settings has vigorously been investigated with these AKI diagnostic criteria developments, we have not acquired any pharmacological agents that are effective for AKI in the clinical. On the other hand, renal replacement therapy (RRT) has been employed as a key clinical intervention for severe AKI patients with life-threatening critical illness. However, we have not obtained any clear evidence regarding the optimal timing of RRT initiation for severe AKI.