Blood Transfusion

Overview

During a blood transfusion, a blood component (a part of whole blood) is put into the bloodstream. The blood used in a transfusion is compatible with the blood type of the person receiving the blood and moves into the body through an intravenous (IV) line, usually inserted in the arm.

A person rarely receives a whole-blood transfusion. Usually, a blood component such as red blood cells, platelets or plasma is given. Some may receive a combination of components. The type of component given depends on the medical condition.

There are four main blood types, which are classified as A, B, AB, and O. All blood is also classified according to its Rh factor. The Rh factor refers to the presence or absence of a specific antigen in the blood. (An antigen is a substance capable of stimulating an immune response.) People are either Rh positive or Rh negative, meaning they either have the antigen or they do not.

Red blood cell transfusions

A red-blood-cell transfusion increases the number of red blood cells in the body. Red blood cells carry oxygen from the lungs to all parts of the body and return carbon dioxide from the body to the lungs. Certain factors, such as anemia, bleeding, chemotherapy, and radiation treatments, can decrease red blood cells. A decrease in red blood cells means less oxygen is being transported throughout the body. When the body receives less oxygen, people may feel tired, weak, dizzy, or light-headed. A transfusion of one unit of red blood cells usually takes 90 minutes to two hours, but may take longer.

Platelet transfusions

A platelet transfusion increases the number of platelets in the body. Bone marrow makes platelets that circulate in the blood. The spleen temporarily stores some of the platelets. Platelets help clot blood and repair injured blood vessels. When someone is bleeding, platelets go to the injured site, clump together, and stop the bleeding. A platelet transfusion takes about 60 to 90 minutes.

Conditions that affect the bone marrow or spleen can affect how many platelets a person has and their body's 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 platelets are low, blood will not clot in its usual way.

Plasma transfusion

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