The criteria for blood transfusion are symptoms such as massive blood loss, coagulation abnormalities, severe infection, anemia or hypoproteinemia. Massive blood loss: when blood loss accounts for 10%~20% of total blood volume, a small amount of plasma substitute can be input; when blood loss accounts for 20%~30% of total blood volume, concentrated red blood cells should be input appropriately; when blood loss accounts for 30%~50% of total blood volume, half of whole blood and concentrated red blood cells can be transfused, followed by crystal colloid solution and plasma; when blood loss accounts for more than 50% of total blood volume, a large amount of blood transfusion should be given. Coagulation abnormality: In clinical practice, fresh frozen plasma is sometimes entered in order to prevent and treat bleeding due to coagulation abnormality. Severe infections: In refractory infections with poor antibiotic therapy and low neutrophils, concentrated granulocytes are entered to control the infection. Anemia or hypoproteinemia: In cases of insufficient synthesis of albumin and increased destruction of red blood cells, patients should be transfused with red blood cell concentrates to correct anemia, supplement albumin, or plasma to treat hypoproteinemia, depending on the results of the test. Transfusions should be performed under the supervision of a physician.