One hundred and seventeen patients with 1 of the following risk factors of AKI were randomized into either the control ( n = 57 ) or the NAC ( n = 60 ) group ; ( i ) preoperative serum creatinine > 1.4 mg/dL ; ( ii ) left ventricular ejection fraction < 35 % or congestive heart failure ( iii ) age > 70 years ( iv ) diabetes or ( v ) re-operation .