The purpose of this study is to determine the possible effect nephroprotective of N-acetylcysteine in patients with chronic kidney disease undergoing elective coronary artery bypass grafting by serial evaluation of renal function and to evaluate whether treatment reduces cardiac mortality, cardiac events and Global mortality, if it interferes with oxidative stress and inflammation and the need for dialysis.

Renal failure is a serious and relatively frequent complication of cardiac surgery was observed, especially in diabetics and those with pre-existing renal dysfunction. Given that oxidative stress is elevated in diabetics and in renal and heart, it is reasonable to speculate on its involvement in the pathophysiology of this complication. It is unknown whether the incidence of postoperative renal failure can be reduced by antioxidants. N-acetylcysteine (NAC) is an antioxidant that prevents nephropathy induced by contrast medium and aminoglycosides and increases intracellular levels of cyclic guanosine monophosphate, acting as a vasodilator and platelet inhibitor.

Based on a knowledge of the pathophysiology of ARF, several interventions have been attempted over the past decades. However, various measures employed successfully in the prevention of experimental ARF did not result in success in clinical practice. Much of this failure is probably due to the difference between the experimental models of ARF that encountered in the clinic. Other factors that should be considered, and that may explain the poor results in clinical trials are: the time of use of the drug, dosage and route of administration, are not always adequate.

From the data in the literature, it remains doubtful whether the protective role of NAC is limited only to contrast nephropathy or whether it could have application in other clinical situations in which oxidative stress and vasoconstriction are determinants of injury, as occurs, for example, in CABG surgeries.

NAC is a drug of low cost and low toxicity, this paper intend to assess its role as prophylaxis of renal dysfunction in the postoperative period of CABG in patients with chronic kidney disease stages 3 and 4 (GFR between 15 and 59 mL/min/1, 73 m2 of body surface).

Inclusion Criteria:

• adult patients aged 30 to 80 years old of both sexes
• indicated for elective CABG
• with glomerular filtration rate, assessed with the MDRD <60 mL/min/1, 73 m2 and> 15 mL / min / 1.73 m2 body surface

Exclusion Criteria:

• patients on chronic dialysis or with creatinine> 5 mg / dL preoperatively; individuals allergic or intolerant to N-acetylcysteine
• pregnant women
• patients with cancer
• patients underwent re-surgery within the first 72 hours postoperatively