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Primary hip arthroplasty has an average blood loss of one to two pints, while revision hip arthroplasties can be as much as four pints of blood loss. Knee arthroplasty is usually performed with a tourniquet on the leg and results in an almost bloodless procedure. However, the major blood loss from total knee arthroplasty occurs after the wound is closed and can be as much as a primary total hip arthroplasty. Therefore, the average blood loss for joint arthroplasty is approximately two pints.1

One of the many functions of blood is to supply the tissues with oxygen. If tissues (wounds, skin, heart, muscles, etc) are deprived of oxygen, there is a tremendous strain on the body and these tissues could die. Therefore, a large blood loss could result in poor healing of the surgical wound, affect progression in physical therapy, or even cause a heart attack or stroke.

The surgeon, together with the anesthesiologist, can minimize blood loss during the operation. The better the surgeon prepares for the operation the quicker the procedure can be performed which can limit the duration of bleeding.2 In addition, the surgeon must perform a careful dissection through the tissues to insure meticulous hemostasis and pack areas of peak bleeding with sponges. The anesthesiologist uses surgical monitoring to determine the blood loss and prevent fluctuations in blood pressure. By maintaining a constant low blood pressure (usually a 35% reduction in the patient's baseline blood pressure), the anesthesiologist prevents uncoagulated blood vessels from bleeding and reduces blood loss. Hypotensive anesthesia has been shown to reduce blood loss by 43% when compared to those patients who underwent joint replacement surgery under normotensive anesthesia.2

Patients should be transfused blood when they become symptomatic, i.e. unstable vital signs: very low blood pressure, high heart rate, chest pain related to insufficient oxygen delivery to the heart because of a low hemoglobin (substance in the red cells in blood that delivers oxygen to tissues). The hemoglobin (hgb) is measured before the procedure to determine the patient's baseline status; normal hgb levels range from 12 to 18 g/dL. However, those with impaired cardiopulmonary function have a reduced tolerance for a lower hgb and the morbidity rates increase as the postoperative hgb decreases. Therefore, those patients with a history of a myocardial infarction (heart attack), congestive heart failure, unstable angina (chest pain), stroke, or uncontrolled hypertension cannot tolerate as low a hemoglobin as a healthy person. Data has shown that healthy patients can tolerate hemoglobin levels of 5 to 7 g/dL (hematocrit of 15-21%).3 However, there is no "magic number" used for transfusing patients when the hemoglobin is low; the decision to transfuse is based on the patient's medical history and clinical symptoms.

Allogenic blood is blood that is donated from a person other than the patient. Blood transfusions can be avoided by a concerted effort from the entire medical team: the orthopaedic surgeon, anesthesiologist, and the internist. The orthopaedic surgeon can increase the speed of the surgery by being well prepared, ensuring that the proper implants are available and by performing proper surgical technique. Spinal anesthesia reduces blood loss during total joint arthroplasty, as well as hypotensive anesthesia.2 The internist can ensure that the patient is in optimum health before the surgery by adjusting medications and supplying vitamins and iron to maximize the patient's ability to make more hemoglobin.

Autotransfusion requires preplanned donation for the patient's blood before the surgery, called autologous blood. The shelf life of this blood is approximately 35 days and is usually donated four weeks before the surgery to allow the patient's body to compensate and "rebuild" its hemoglobin.

Intraoperative blood salvage requires an agreement among the patient, physician, anesthesiologist, and the individual operating the salvage unit. The blood is collected during the operation with suctioning devices and sponges, and then placed in a special container that processes the blood so that it is safe for transfusion back into the patient.