To prevent blood clots, an intravenous drug called heparin is used. This prevents the blood from clotting and could result in blood loss. There could even be enough blood loss to need a blood transfusion.
Many doctors advise patients to donate their own blood at least three weeks before the surgery. Family members can also be tested and donate on your behalf. Blood testing for hepatitis has reduced problems with blood transfusion as a source for hepatitis. Likewise, donor screening has reduced the risk of HIV by infusion. This risk is very low (one in one million transfusions).
There’s also a new drug out called Epogen that can increase red blood cells. This has reduced the need for blood transfusion for many patients having joint replacement surgery.