The purpose of this trial is to study the use of nesiritide in thoracic aneurysm repair to prevent acute renal failure.

The study hypothesis: Nesiritide, given prophylactically prior to surgery may prevent acute renal failure requiring dialysis and/or decrease mortality.

Acute renal failure is a major and serious complication of more than 200,000 cardiovascular surgeries performed on adult Americans annually (www.sts.org). 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.

The overall postoperative mortality rate for cardiovascular surgery is 2.2%, but is much higher for thoracic aortic aneurysm surgery (8-10% for elective repair, 25-50% for ruptured thoracic aorta aneurysm repair). The major risk factor for thoracic aortic aneurysm surgery related mortality is post-operative ARF requiring dialysis. When thoracic aortic aneurysm surgery is complicated by acute renal failure, the mortality rate worsens to 50%. Thus, identifying ways to prevent acute renal failure may have a major impact on the outcome of cardiovascular surgery. A retrospective study of the use of nesiritide in cardiovascular surgery patients by our group has demonstrated a tendency towards a decreased incidence of renal failure and mortality, when the medication is used prophylactically.

Inclusion Criteria:

• Age 18 years or older
• Undergoing thoracic aortic aneurysm surgery
• Impaired renal function

Exclusion Criteria:

• Prior history of allergy/adverse reaction to Nesiritide
• History of any organ transplant
• Preoperative intra-aortic balloon pump (IABP)
• Decompensated congestive heart failure (CHF)