(a) RIFLE classification [11]

RIFLE category	SCr/GFR criteria	Urine output criteria
Risk	↑ SCr ≥150–200% (1.5–2 fold) OR decrease of GFR >25%	Urine output <0.5 mL/kg/hour for 6 hours
Injury	↑ SCr >200–300% (>2-3 fold) OR decrease of GFR >50%	Urine output <0.5 mL/kg/hour for 12 hours
Failure	↑ SCr >300% (>3 fold) from baseline or decrease of GFR >75% OR serum creatinine ≥4 mg/dL with an acute rise of ≥44 μmol/L	Urine output <0.3 mL/kg/hour for 24 hours or anuria for 12 hours
Loss	Complete loss of renal function for >4 weeks
End stage kidney disease	Need for RRT for >3 months