The purpose of the study is to evaluate kidney biomarkers and determine if there is a correlation between Erythropoietin (EPO) levels and acute kidney injury after cardiac surgery. An early biomarker for kidney injury may be helpful in identifying, monitoring and managing patients at risk for kidney failure after cardiac surgery. To evaluate Erythropoietin's role as a predictor of poor renal function in the immediate post-bypass period we plan to compare EPO levels to Neutrophil gelatinase-associated lipocalin (NGAL).

Acute kidney injury (AKI) is a serious complication after cardiac surgery and cardio-pulmonary bypass. AKI is associated with high mortality.

Erythropoietin, a hormone produced by the kidneys, will be evaluated as a potential biomarker of kidney injury. Neutrophil gelatinase-associated lipocalin (NGAL) has been studied as a biomarker of kidney injury. Early kidney injury detection has been long sought and NGAL has been shown to be a promising biomarker. A troponinlike biomarker of AKI that is easily measured and capable of both early detection and risk stratification would represent an advancement in our ability to differentiate acute kidney injury from failure.

Investigating EPO as a biomarker may prove to have increased predictive value in the clinical care of cardiac surgery patients.

Inclusion Criteria:

• Cardiac surgery with cardiopulmonary bypass with DHCA
• Normal renal function or renal insufficiency-serum creatinine less than 2.5 mg/dL
• Adult male and female patients 18 years and older

Exclusion Criteria:

• VADS
• Emergent cases
• Prolonged hypoxemia before, during or after bypass
• End stage renal disease
• Patients receive erythropoietin receptor agonists

Cardiac surgery patients.