Blood components are obtained from blood collected from volunteer blood donors. Blood donation programs exist to allow blood to be donated by a patient for themselves, by anonymous donors or, in some situations, by someone specified by the recipient.
Blood may be processed into any of these various blood components:
Whole blood contains red blood cells and plasma. Whole blood is often used for open-heart surgery and may also be used for exchange transfusions (complete replacement of a baby's blood) in newborns with hemolytic disease of the newborn. This product is otherwise not commonly used.
Packed Red Blood Cells
Red blood cells carry oxygen to the tissues. Packed red blood cells have had most of the plasma removed from the whole blood. Packed cells are usually given into a vein over two to four hours to replace the red cells lost through bleeding, hemolysis (destruction of the red blood cells), or decreased production of red cells by the bone marrow. The decreased production of cells may be due to bone marrow failure, cancer involving the marrow, or the effect of chemotherapy drugs used to treat a cancer.
Fresh Frozen Plasma
Fresh frozen plasma is plasma which was frozen and stored shortly after it was obtained from the blood donor. Fresh frozen plasma contains many clotting factors and is often used alone or with cryoprecipitate to replace the low levels of clotting factors. It is usually given into a vein over one to two hours.
Platelets are the cell fragments which prevent or stop bleeding or bruising by physically plugging the hole in the blood vessel. Platelets are usually given into a vein over a few minutes to an hour. If a patient's bone marrow is not producing platelets, then platelet transfusions are usually needed once or twice a week, or even more often. Platelets may also be given when a patient's platelets are not functioning properly due to medicines, illness or mechanical damage (such as from an artificial heart valve).
Cryoprecipitate is the part of the blood which contains only certain clotting factors such as factor VIII (deficient in hemophilia A), von Willebrand factor, and fibrinogen. Currently, cryoprecipitate is usually given only as a source of fibrinogen (necessary for forming a clot). Some patients with certain types of hemophilia or patients who lack fibrinogen may receive cryoprecipitate to treat their clotting defect. Also, severely ill patients may develop an abnormal clotting condition known as DIC (disseminated intravascular coagulation), which can cause a decrease in the body's clotting factors and result in severe bleeding. Cryoprecipitate along with fresh frozen plasma (see above) may be given to help replace the clotting factors that are low. Cryoprecipitate is usually given over just a few minutes to an hour into a vein.
Granulocytes, also called neutrophils, are the cells which help fight off bacterial or fungal infections. Granulocytes are very occasionally given to help fight off severe infections in patients who have very low numbers of granulocytes in the blood and have not responded to medications. Most often granulocytes are given daily for five days or until the patient's granulocyte count returns to a level which allows the patient to fight the infection on his or her own. Granulocytes are usually infused into a vein over one to two hours.