 Acute renal failure is a major and serious complication of more than 200,000 cardiovascular surgeries performed on adult Americans annually The incidence of acute renal failure ARF after cardiac surgery depending on criteria used to define ARF is 1-5, in the absence of preexisting renal dysfunction. The subset of patients with thoracic aortic aneurysm surgery have a higher risk for the development of postoperative ARF 25-40 - ARF defined as doubling of serum creatinine; 13 - ARF defined as requirement for dialysis. This risk is further increased by various peri-operative factors, especially cardiopulmonary bypass time. 