Ischemic reperfusion injury of cardiopulmonary bypass and postoperative renal dysfunction is a common problem which influence poor outcome in subjects undergoing valvular heart surgery. The incidence of postoperative renal dysfunction was reported as high as 7~8% in heart surgery using bypass, and is thought to be caused by ischemia/reperfusion injury. Remote ischemic postconditioning was also reported to be protective for ischemic/reperfusion injury in previous animal studies and stoke patients. Therefore, the investigators are trying to evaluate the clinical effect of remote ischemic postconditioning on postoperative renal dysfunction in subjects undergoing valvular heart surgery with bypass.

Inclusion Criteria:

• patients who are undergoing valvular heart surgery
• Adult
• age 19-80

Exclusion Criteria:

• peripheral vascular disease with circulation deterioration
• Renal replacement therapy
• preconditioning medication
• Myocardiac infarction within 3 weeks
• active infective endocarditis
• high dosage steroid therapy
• mental retardation
• unlettered person