People who undergo coronary artery bypass grafting (CABG) or heart valve surgery may experience acute kidney injury (AKI) after their surgery. Current medical tests cannot identify AKI until approximately 48 hours after it occurs. This study will examine three new biomarkers in blood and urine that may provide a more effective and faster way of predicting AKI in people who undergo CABG or heart valve surgery.

AKI, which is indicated by a sudden change in serum creatinine levels, is a serious complication that can occur after a patient undergoes CABG or heart valve surgery. People who experience AKI after heart surgery may be at increased risk for post-operative complications, including long-term kidney failure or heart damage. AKI is currently identified by testing serum creatinine levels in the blood, which is the traditional marker of kidney function. However, serum creatinine levels can be affected by other non-kidney-related factors and may not positively identify AKI until 48 hours after it begins. This study will examine three new biomarkers found in urine and blood-urine interleukin 18 (IL-18), neutrophil gelatinase-associated lipocalin (NGAL), and cystatin C-that may be able to predict AKI more effectively and faster than serum creatinine levels. In addition, study researchers will also determine if changes in these biomarkers can predict the severity of AKI more successfully than serum creatinine tests.

This study will enroll people undergoing CABG or heart valve surgery at Yale-New Haven Hospital. Before the surgery and once a day for 5 days after the surgery, blood and urine collection will occur. Study researchers will also review participants' medical records. Twelve months after hospital discharge, participants will return to the clinic for a follow-up visit for repeat blood and urine collection and to complete questionnaires. A portion of blood will be saved for future genetic testing; this is optional.

Inclusion Criteria for Adults: (must have at least one of the following)

• Emergent surgery
• Pre-existing kidney impairment (baseline serum creatinine greater than 2 mg/dL)
• Ejection fraction less than 35%
• At least 70 years old
• Diabetes mellitus
• Combined CABG and valve surgery
• Repeat CABG or valve surgery

Exclusion Criteria for Adults:

• Pre-operative acute kidney injury
• Enrolled in a conflicting research study
• Prior kidney transplantation
• Baseline serum creatinine level greater than 4.5 mg/dL
• Nephrotoxic drugs administered pre-operatively
• Surgery for only left ventricular assist device

Inclusion Criteria for Children:

• Undergoing open heart surgery

Exclusion Criteria for Children:

• Pre-existing acute kidney failure (greater than 50% decline in creatinine clearance)

1. Adults undergoing CABG surgery or heart valve surgery.
2. Children undergoing cardic surgery (requiring CABG) to correct congenital heart defects.