It is not uncommon to see stories in the media about blood shortages in a city that force the cancellation of some surgeries, while other stories report an increase in infectious diseases due to blood transfusions. Should I have a blood transfusion for an artificial joint replacement? How can transfusions be avoided or reduced? About half of the patients need blood transfusions. Both knee and hip replacements will bleed more or less because they involve bone trauma, and the blood vessels in bone trauma do not contract and close on their own, so there is more bleeding in artificial joint surgery than in general surgery. The amount of bleeding is not only related to the type of prosthesis used, but also to the surgeon’s technique and habits. When performing an artificial knee replacement, most surgeons prefer to operate with a tourniquet, when there is generally no bleeding during the operation, and only afterwards. Overall, about half of all artificial joint replacement patients require blood transfusions. The job of blood is to bring nutrients and oxygen to the tissues, while taking metabolites and carbon dioxide from the tissues to the kidneys or lungs to be excreted. When the body loses blood, the amount of blood in the body is insufficient and may need to be replenished, but not necessarily by transfusion because the body has certain compensatory functions, for example, the heart can work faster to make up for the lack of blood in the body. So what are the situations that require blood transfusion? There are two situations. In this case, the patient has lost 1/5 to 1/3 of his own blood and his hematocrit has dropped to 60-80 grams per liter. Secondly, the patient’s heart function is poor, if the heart work accelerates too much it may lead to heart attack, at this time the patient’s hematocrit may need blood transfusion even if it is higher than 60-80 grams/liter. Blood transfusion is risky, and autologous blood transfusion becomes the first choice. Blood transfusion can increase the patient’s ability to carry oxygen in the blood, so that the heart does not have to work “hard” to meet the needs of the body, but blood transfusion may also bring many problems, such as: fever, allergies, hemolysis and other immune reactions, which can cause death in serious cases; too much blood transfusion can cause excessive load on the heart. If the donor has infectious diseases such as AIDS or hepatitis in his body, blood transfusion can infuse the donor’s disease to the patient receiving the transfusion. Because of these risks and the tight supply of allogeneic blood, many hospitals are now performing “autologous transfusions”. Blood that is lost during and after surgery can be recovered, processed and transfused back to the patient. The patient’s own blood is collected and stored several days before or at the beginning of the surgery, and after the blood is collected, the patient drinks water or is given ordinary fluids, so that the patient’s blood is first diluted, and the blood lost during the surgery is diluted to a low concentration, and then the stored autologous blood is transfused back to the patient when needed. The biggest advantage of autologous blood transfusion is that it does not cause infectious diseases or transfusion reactions due to blood transfusion. The conditions for preoperative storage of autologous blood are that the patient is in good general health and has a hematocrit of 110 g/L or more. The surgeon will also try to avoid blood transfusion through improvements in surgical techniques, such as the use of an electric knife to cut tissue during surgery and the use of a tourniquet to block blood flow to the limb during knee surgery. The anesthesiologist will also lower the patient’s blood pressure appropriately to reduce bleeding. Blood transfusions can speed up a patient’s recovery, but they may also pose risks to the patient, so it is best to follow the doctor’s advice as to whether a transfusion is necessary.