Inclusion Criteria:

• * Presenting for cardiac surgery at the Mayo Clinic in Rochester, Minnesota.
• * Scheduled to undergo complex cardiac surgery with the use of cardiopulmonary bypass. Complex cardiac surgery will be defined as surgery involving more than one heart valve, redo-sternotomy procedures, or combined valvular and coronary artery bypass graft procedures (aortic repair not excluded if meets other criteria).

Exclusion Criteria:

• * Left or right ventricular assist device implantation or explantation.
• * Procedures not requiring cardiopulmonary bypass.
• * Active infection or sepsis requiring antimicrobial therapy and/or vasopressor therapy (treated endocarditis is not excluded).
• * Severe hepatic disease resulting in ascites.
• * Pre-operative significant renal dysfunction including a baseline creatinine equal to or greater than 2 mg/dL or requiring dialysis.
• * Immunosuppressive medication use (including current IV or oral steroids use, use of anti-rejection medications for transplant within 1 month, or chemotherapy within 6 months).
• * Immunodeficiency syndrome including HIV/AIDS, leukemia, and multiple myeloma