Guidelines for blood transfusion have been issued for years. According to these guidelines, red blood cells (RBCs) transfusion should be given when the hemoglobin level is less than 6g/dL or 7g/dL and is unnecessary when the level is more than 10g/dL. However, in all the guidelines, the determination of whether RBCs should be administered when the hemoglobin level is in the range of 7~10g/dL is based on the judgment from anesthesiologists or surgeons. Index of transfusion trigger for patients with hemoglobin level between 7/dL and 10g/dL is necessary and important in clinical practice. Based on the aim of blood transfusion that maintain the balance of oxygen supply and oxygen consumption, the investigators hypothesize that index of transfusion trigger for patients with hemoglobin level between 7/dL and 10g/dL could be calculated by their history about heart and blood pressure, and routine monitoring parameters including pulse oximetry, temperature, and the use of vasoactive medications. To verify this hypothesis, the investigators present West China Perioperative Transfusion Score (WCPTS) for the trigger of transfusion according to the patient's history and monitoring parameters, and the investigators design a randomized controlled clinical trial to test this score.