Inclusion Criteria:

- Chinese Han unrelated population

- undergoing elective cardiac surgery with CPB

Exclusion Criteria:

- malignant tumor

- autoimmune disease, immunodeficiency or immunosuppressive therapy

- chronic renal disease (glomerular filtration rate < 60ml/(min•1.73m2)) or liver
dysfunction (Child Pugh classification>A)

- COPD, tuberculosis or other chronic pulmonary diseases

- anemia with hemoglobin lower than 90mmHg

- bleeding disorders

- postoperative pericardial tamponade requiring re-operation

- postoperative low cardiac output syndrome or acute pulmonary edema after left cardiac
failure.