A 76-year-old female was hospitalized because of congestive heart failure and anemia. A thorough examination led to a diagnosis of severe aortic stenosis and cold agglutinin disease. The critical temperature for hemagglutination was 27 °C, which caused particular problems with regard to the myocardial protection temperature during surgery. Aortic valve replacement was performed safely by increasing the normal myocardial protection temperature from 15 °C to 32 °C and using 3 times the normal volume of cardioplagic fluid. As a result of strict perioperative thermal management, the operation was completed without any complications.