Transfusion Health Article

Definition

Transfusion is the process of transferring whole blood or blood components from a donor to a recipient.

Purpose

Transfusions are given to restore lost blood, to improve clotting time, and to improve the ability of the blood to deliver oxygen to the body's tissues. About 32,000 pints of donated blood are transfused each day in the United States.

In the United States, blood collection is strictly regulated by the Food and Drug Administration (FDA). The FDA has rules for the collection, processing, storage, and transportation of blood and blood products. In addition, the American Red Cross, the American Association of Blood Banks (AABB), and most states have specific rules for the collection and processing of blood. The main purpose of regulation is to ensure the quality of transfused blood and to prevent the transmission of infectious diseases through donated blood. Before blood and blood products are used, they are extensively tested for such infectious agents as hepatitis and human immunodeficiency virus (HIV).

Blood and its components

Either whole blood or its components can be used for transfusion. Most blood collected from donors is broken down (fractionated) into components that are used to treat specific problems or diseases. Treating patients with fractionated blood is the most efficient way to use the blood supply.

WHOLE BLOOD. Whole blood is used exactly as received from the donor. Blood components are parts of whole blood, such as red blood cells (RBCs), white blood cells (WBCs), plasma, platelets, clotting factors, and immunoglobulins. Whole blood is used only when needed or when fractionated components are not available, because too much whole blood can raise the recipient's blood pressure. Use of blood components is a more efficient way to use the blood supply, because blood that has been fractionated can be used to treat more than one person.

Whole blood is generally used when a person has lost a large amount of blood. Such blood loss can be caused by injury or surgical procedures. Whole blood is given to help restore the blood volume, which is essential for maintaining blood pressure. It is also given to ensure that the body's tissues are receiving enough oxygen. Whole blood is occasionally given when a required blood fraction is unavailable in isolated form.

RED BLOOD CELLS. Red blood cells (RBCs) carry oxygen throughout the body. They pick up oxygen as they pass through the lungs and give up oxygen to the other tissues of the body as they are pumped through the arteries and veins. When patients do not have enough RBCs to properly oxygenate their bodies, they can be given a transfusion with RBCs obtained from donors. This type of transfusion will increase the amount of oxygen carried to the tissues of the body. RBCs are recovered from whole blood after donation. They are then typed, removed from the watery blood plasma to minimize their volume (packed), and stored. RBCs are given to people with anemia (including thalassemia), whose bone marrow does not make enough RBCs, or who have other conditions that decrease the number of RBCs in the blood. Occasionally, red blood cells from rare blood types are frozen. Once frozen, RBCs can survive for as long as ten years. Packed RBCs are given in the same manner as whole blood.

WHITE BLOOD CELLS. White blood cells (WBCs) are another infection-fighting blood component. On rare occasions, white blood cells are given by transfusion to treat life-threatening infections. Such transfusions are given when the WBC count is very low or when the patient's WBCs are not functioning normally. Most of the time, however, antibiotics are used in these cases.

PLASMA. Plasma is the clear yellowish liquid portion of blood. It contains many useful proteins, especially clotting factors and immunoglobulins. After plasma or plasma factors are processed, they are usually frozen. Some plasma fractions are freeze-dried. These fractions include clotting factors I through XIII. Some people have an inherited disorder in which the body produces too little of the clotting factors VIII (hemophilia A) or IX (hemophilia B). Transfusions of these clotting factors help to stop bleeding in people with hemophilia. Frozen plasma must be thawed before it is used; freeze-dried plasma must be mixed with liquid (reconstituted). In both cases, these blood fractions are usually small in volume and can be injected with a syringe and needle.

PLATELETS. Platelets are small disk-shaped structures in the blood that are essential for clotting. People who do not have enough platelets (a condition called thrombocytopenia) have bleeding problems. People who have lymphoma or leukemia and people who are receiving cancer therapy do not make enough platelets. Platelets have a very short shelf life; they must be used within 5 days of blood donation. After a unit of blood has been donated and processed, the platelets in it are packed into bags. A platelet transfusion is given in the same manner as whole blood.

IMMUNOGLOBULINS. Immunoglobulins are the infection-fighting fractions in blood plasma. They are also known as gamma globulin, antibodies, and immune sera. Immunoglobulins are given to people who have difficulty fighting infections, especially people whose immune systems have been depressed by such diseases as AIDS. Immunoglobulins are also used to prevent tetanus after a cut has been contaminated; to treat animal bites when rabies is suspected; or to treat severe childhood diseases. Generally, the volume of immunoglobulins used is small, and it can be injected.