This is a randomized, double-blinded, placebo-controlled trial to evaluate fenoldopam and N-acetylcysteine (NAC) individually, and together, as renal protective agents for patients with renal insufficiency undergoing heart surgery. Subjects have chronic renal insufficiency with creatinine clearance (CrCl) </= 40cc/min but not on pre-operative dialysis, and receive: NAC 600 mg by mouth (po) twice a day (bid) or placebo starting 24 hours pre-operative and continuing through the day of surgery; and/or fenoldopam 0.1 mcg/kg/min intravenous (IV) or saline placebo at anesthetic induction and continuing for 48 hours. Outcome data include: nadir, post-operative day 3 and post-operative day 14 CrCl, time to CrCl nadir, length of Intensive Care Unit (ICU) stay, length of post-operative hospital stay, hospital costs, mortality, and the need for hemodialysis. Intraoperative and post-operative pressor use is being monitored. The enrollment will include 80 patients (20 in each group).