Contrast induced nephropathy (CIN) is a common cause of renal failure associated with prolonged hospitalization, significant morbidity or mortality, and cost. CIN has been reported to account for 10% of hospital acquired renal failure. Several strategies or medications were tried to prevent CIN. Of these, mucomyst and normal saline infusion are effective to prevent CIN. Sodium bicarbonate has shown mixed results from recent randomized trials. Moreover,limited data have been available for preventing CIN in diabetic renal dysfunction undergoing coronary angiography or intervention. Our hypothesis is that addition of sodium bicarbonate will be more efficacious than normal saline in preventing CIN at above situation.