- The investigators defined 'at risk' to include patients with at least one of the following at the time of randomization (i) a serum creatinine of > 106 µmol/L and or urea > 6 mmol/L, (ii) urine output of < 0.5 cc/kg over > 4 hrs or (iii) an increase in serum creatinine of > 50 µmol/L in < 24 hours.