American Medical Association Family Medical Guide - American Medical Association [367]
Blood Transfusions
If your blood level is low as the result of disease or bleeding (especially from surgery or a severe injury), you may be given a blood transfusion to bring your blood up to a healthy level. A transfusion consists of red blood cells if you have anemia (see page 610) or platelets (which enable blood to clot) if you have bleeding (thrombocytopenia; see page 620).
Blood Donors
Although researchers continue to look for ways to make synthetic blood substitutes, for now people who volunteer to be blood donors are the only sources of blood and blood products. AIDS has highlighted the importance of testing the blood of potential donors for bloodborne infectious organisms such as HIV, hepatitis B and C, malaria, and syphilis.
Before giving blood, all donors are given a blood test to make sure they don’t have anemia. If their blood is found to be healthy, about 1 pint of blood is removed from one of their veins with a needle. This procedure takes about 10 to 20 minutes and is painless and safe. Giving blood does not expose a donor to HIV or any other disease-causing organism because new, sterile needles are used for each donor.
Having a blood transfusion
Self-donation, also called autologous blood donation, is an alternative to using blood from donors. People can donate their own blood in the few weeks before they have a scheduled surgical procedure. During this time, their bone marrow makes new blood to replenish the supply. The donated blood may be stored and used during or after the surgery if needed. An autologous blood donation eliminates the problems of matching blood types and the risk of infections. In directed blood donations, people can select a donor, such as a relative or friend, who gives blood to be used specifically for them.
Blood Groups and Blood Matching
Transfusions are safe and effective if the donor and recipient have compatible blood types. Blood is categorized into four main groups—A, B, AB, and O. In most blood groups, the surfaces of red blood cells are coated with specific proteins called antigens, which are labeled A or B. A person’s blood cells have either A or B antigens (A or B blood group), both antigens (AB blood group), or neither antigen (O blood group). In the plasma, a person with A antigens has antibodies against B antigens and a person with B antigens has antibodies against A antigens, which cause a reaction when combined. People with type O blood do not have the A or B antigens to cause a reaction with other blood. For this reason, people with type O blood can donate their blood to people with any other group without causing a reaction. People with AB blood can safely receive A, B, or O blood. Other blood classifications, including Rhesus (Rh) factor (see page 508), are made to ensure a compatible match between donor and recipient.
The blood groups of donor blood are recorded on each unit of blood to make sure that a person having a transfusion gets the right type of blood. Before each transfusion, small quantities of the recipient’s and the donor’s blood are combined in the laboratory to ensure that they are compatible and that the transfusion is safe.
Thalassemia
Thalassemia is a group of blood disorders caused by an inherited genetic defect that blocks the formation of hemoglobin A, the type of hemoglobin in the red blood cells of healthy adults. Hemoglobin is the oxygen-carrying protein in blood. Hemoglobin A is formed by a combination of four proteins—two alpha proteins and two beta proteins—that enable red blood cells to carry oxygen to tissues. Thalassemia is the most common blood