Default composition was sodium 142 mEq/l, bicarbonate 33 mEq/l, calcium 2.6 mEq/l, and magnesium 1.4 mEq/l. Intermittent hemodialysis was performed for four hours except for the first and second sessions with a dialysate flow of 500 ml/min and blood flow of 200 ml/min [18], using low-flux polysulfone hemofilters AZD9291 clinical trial (KF-18C, Kawasumi Laboratories, Shinagawa-ku, Tokyo, Japan). Double lumen catheters were placed as vascular access.In the ICUs, the indications for RRT initiation were: (1) azotemia (BUN > 80 mg/dL and sCr > 2 mg/dl) with uremic symptoms (encephalopathy, nausea, vomiting, etc); (2) oliguria (urine amount < 200 ml/8 hours) or anuria refractory to diuretics; (3) fluid overload refractory to diuretics use with a CVP level above 12 mmHg or pulmonary edema with a partial pressure of arterial oxygen/fraction of inspired oxygen ratio below 300 mmHg; (4) hyperkalemia (sK+ > 5.

5 mmol/L) refractory to medical treatment; and (5) metabolic acidosis (a pH < 7.2 in arterial blood gas) [13,18]. We recorded all the indications of patients upon RRT initiation.CovariatePatients were categorized into two groups (early dialysis (ED) and late dialysis (LD)) according to their RIFLE (Risk, Injury, Failure, Loss, and End stage) classification [24] (Table (Table1)1) before RRT initiation. The RIFLE classification was first proposed by the Acute Dialysis Quality Initiative group in an attempt to standardize AKI study, and the scores could be used to predict the mortality after major surgery [25,26].

There were many studies comparing the prognoses among patients in different categories of RIFLE classification, but only a few studies [27,28] compared the outcome among patients who initiated RRT in different categories of RIFLE classification. As in previous studies [27,29,30], we used ‘simplified’ RIFLE (sRIFLE) classification with only GFR criterion applied for classification because the eight-hourly urine volumes in our database could not match the 6- or 12-hourly urine output criterion in RIFLE classification. Those who initiated RRT when in sRIFLE-R (risk) or sRIFLE-0 [26], which means not yet reaching the sRIFLE-R level were defined as ‘ED’, while in sRIFLE-I (injury) or sRIFLE-F (failure) were classified as ‘LD’.

The baseline sCr was the data obtained at hospital discharge from the previous admission in those who had more than Brefeldin_A one admission [29], or the data estimated using the Modification of Diet in Renal Disease (MDRD) equation [31] in those with only one admission (assuming an average GFR of 75 ml/min/1.73 m2). The peak sCr was defined as the highest sCr before RRT initiation in ICUs. The GFR were estimated using the isotope dilution mass spectrometry–traceable four-variable MDRD equation [31].Table 1RIFLE classification [24] for acute kidney injuryOutcomesThe endpoint of this study was in-hospital mortality.