Blood Transfusion

Blood Components of Blood Transfusion Therapy

Whole blood consists of plasma, red blood cells, white blood cells, and platelets. Plasma makes up 55 percent of total blood volume; red blood cells, white cells, and platelets compose the remaining 45 percent.

Donated blood is nearly always separated into components. A person rarely receives a whole-blood transfusion. Usually, a blood component such as plasma or red blood cells is given. Patients also may receive a combination of components. The type of component patients receive depends on their medical condition.

Red blood cells
Red blood cells carry oxygen from the lungs to all parts of the body and return carbon dioxide from the body to the lungs. The lungs then remove the carbon dioxide. Certain factors, such as anemia, bleeding, chemotherapy, and radiation treatments, can decrease red blood cells in a person's body. A decrease in red blood cells means less oxygen is being transported throughout the body. When a patient's body receives less oxygen, he or she may feel tired, weak, dizzy, or light-headed.

A red-blood-cell transfusion increases the number of red blood cells in the body. The transfusion of one unit of red blood cells usually takes 90 minutes to 2 hours, but may take longer.

Platelets
Bone marrow makes platelets that circulate in the blood. The spleen temporarily stores some of the platelets. Platelets help the body clot blood and repair injured blood vessels; for example, when a cut through the skin begins to bleed, platelets go to the injured site, clump together, and stop the bleeding.

Conditions that affect patients' bone marrow or spleen can affect how many platelets they have and their bodies' ability to store platelets. For example, leukemia causes bone marrow to produce too many white blood cells. This causes a decrease in the number of platelets produced. If a person's platelets are low, his or her blood will not clot in its usual way. A platelet transfusion increases the number of platelets in the body, and takes about 60 to 90 minutes to receive.

Fresh frozen plasma
Plasma, the straw-colored fluid of whole blood, contains water, protein, hormones, and blood-clotting factors. The body uses plasma to maintain normal blood clotting and to prevent blood loss. People who bleed excessively or who are missing blood-clotting factors sometimes receive plasma transfusions.

People who are missing certain blood-clotting factors sometimes receive cryoprecipitate, a component of plasma which contains some of the blood-clotting factors a person needs.

Plasma is separated from donated whole blood and frozen to keep it fresh. Plasma is thawed before being transfused.

A plasma transfusion increases the amount of plasma in the body and prevents blood loss by increasing the amount of blood-clotting factors. The transfusion of each bag of plasma takes 30 to 45 minutes.