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A transfusion is putting blood or some part of it into a person’s vein through an intravenous (IV) line.
Transfusions of blood and blood products may be given to a person who is bleeding or who can’t make enough blood cells. Blood transfusions save millions of lives in the United States every year.
People usually donate whole blood – blood taken right out of a vein through a needle. This whole blood may be called a unit or pint of blood, and equals about 450 milliliters or 16.7 ounces. But whole blood is rarely given as a transfusion. Blood has many parts (called components), and each one does a different job. Whole blood is usually separated into red blood cells, platelets, and plasma. Plasma can be further separated into clotting factors and certain proteins. This lets doctors give patients only what they need. It also helps to get the most out of the donated blood.
People with cancer might need blood transfusions because of the cancer itself. For instance:
Cancer treatments may also lead to the need for blood transfusions:
Red blood cell basics
Red blood cells (RBCs) give blood its color. Their job is to carry oxygen from the lungs through the bloodstream to every part of the body. A substance in red blood cells called hemoglobin does this. Then, the red cells bring carbon dioxide (CO2) back to the lungs, where it’s removed from the body when we exhale.
Red blood cells (and all other blood cells) are normally made in the bone marrow, the soft inner part of certain bones. The production of RBCs is controlled by the kidneys. When the kidneys sense that there aren’t enough RBCs in the blood, they release a hormone called erythropoietin that causes the bone marrow to make more.
When red blood cell transfusions are used
Anemia: People who have low numbers of red blood cells (RBCs) are said to have anemia or be anemic. People who have anemia may need RBC transfusions because they don’t have enough RBCs to carry oxygen to all of the cells in the body. (Low iron or vitamin B12 levels are less common causes of anemia in cancer patients.)
A normal hemoglobin level is about 12 to 18 g/dL. A red blood cell transfusion may be suggested if it drops below 8 g/dL. Whether you need a transfusion for anemia depends on many factors, such as how long it took for the anemia to develop and how well your body is able to cope with it. Anemia due to a sudden loss of blood will probably need to be corrected right away. Anemia that develops slowly is less likely to cause problems, because the body has time to adjust to it to some extent. If your hemoglobin level is lower than normal but you’re not dizzy, pale, or short of breath, you may not need a transfusion.
Patients who have certain heart or lung diseases may be more affected by anemia and may need transfusions even if their hemoglobin level is not very low. Other conditions that increase the need for oxygen may also require transfusions.
There are drugs that can treat anemia instead of a transfusion in some patients, but they carry different risks, work slowly, and cost a lot. For more information about anemia and how it’s treated, see Anemia in People With Cancer.
Surgery: Transfusions may be given during or after surgery to make up for blood loss. In some cases, blood lost during surgery can be collected and given back to the patient. See “Intra-operative or post-operative blood salvage” in Alternatives to Blood Transfusion for more on this.
Plasma is the clear, pale-yellow liquid part of blood. It contains proteins (called clotting factors) that help make blood clot. This is important when the body is injured because clots are needed to help seal blood vessels and stop bleeding. Plasma also contains other proteins, such as antibodies, which help fight infection.
Once plasma is separated from the red blood cells, it can be frozen and kept for up to a year. Once thawed, it’s called fresh frozen plasma.
Plasma can be donated in a process called apheresis, or sometimes called plasmapheresis. The donor is hooked up to a machine that removes blood, separates the plasma, and puts it into a special container. The machine returns the red cells and other parts of the blood to the donor’s bloodstream.
When plasma transfusions are used
Plasma is commonly given to patients who are bleeding because their blood is not clotting the way it should. Cancer patients might also be given fresh frozen plasma if they have a problem called DIC (disseminated intravascular coagulation). In this rare condition, all of the clotting factors in the body are used up or broken down. Signs and symptoms (such as excessive bleeding and bruising) and blood tests help the doctor identify DIC.
Platelets are fragments of cells in blood and are another important part of the clotting process. They work with the clotting factors in plasma to help stop bleeding.
Platelets are usually found in the plasma, and like red blood cells, they can be separated from it. A unit of whole blood has only a small volume of platelets. It takes platelets from several units of whole blood to help keep a person from bleeding. A unit of platelets is defined as the amount that can be separated from one unit of whole blood.
Unlike red blood cells, platelets do not have a blood type (see “Blood types” in Getting a Blood Transfusion), so patients can usually get platelets from any qualified donor. For platelet transfusions, 6 to 10 units from different donors (called random donor platelets) are combined and given to adult patients at one time (they are called pooled platelets).
Platelets can also be collected by apheresis. This is sometimes called plateletpheresis. In this procedure, the donor is hooked up to a machine that removes blood, and keeps just the platelets. The rest of the blood cells and plasma are returned to the donor. Apheresis can collect enough platelets so that they don’t have to be combined with platelets from other donors. Platelets collected in this way are called single donor platelets. (You can find more information about this in Donating Blood.)
When platelet transfusions are used
Cancer patients may need platelet transfusions if their bone marrow is not making enough. This happens when platelet-producing bone marrow cells are damaged by chemo or radiation therapy or when they are crowded out of the bone marrow by cancer cells.
A normal platelet count is about 150,000 to 400,000 platelets per microliter (mcL) of blood, depending on the lab. When platelet counts drop below a certain level (often 20,000/mcL), a patient is at risk for dangerous bleeding. Doctors consider giving a platelet transfusion when the platelet count drops to this level or even at higher levels if a patient needs surgery or is bleeding. If there are no signs of bleeding, a platelet transfusion may not be needed even if the platelet count is low.
Different medicines can be used to help with low platelets depending on the cause of the low platelets.
Cryoprecipitate, or "cryo," is the name given to the small fraction of plasma that separates out (precipitates) when plasma is frozen and then thawed in the refrigerator. It has several of the clotting factors found in plasma, but they are concentrated in a smaller amount of liquid. A unit of whole blood has only a small amount of cryoprecipitate, so about 8 to 10 units (from different donors) are pooled together for one transfusion.
When cryoprecipitate transfusions are used
Cryoprecipitate may be given to replace several blood clotting factors such as:
Unless they’re bleeding, people with cancer rarely need cryoprecipitate.
White blood cell basics
Chemotherapy can damage cells in the bone marrow, and patients getting chemo often have low white blood cell (WBC) counts. (The normal range for WBCs is 4,000 to 10,000 per mcL of blood.)
White blood cells, especially the type called neutrophils (NEW-trow-fills), are very important in fighting infections. When patients have low WBC counts, doctors carefully watch the number of neutrophils or the absolute neutrophil count (ANC). Neutropenia is when a person’s ANC goes below 1,000/mcL. People with neutropenia are at risk for serious infections, even more so if the count stays low for more than a week.
When white blood cell transfusions are used
White blood cell transfusions are given rarely. Research does not show that giving white blood cell transfusions lowers the risk of death or infection in people with low white blood cell counts or white blood cells that are impaired.
Instead of transfusing WBCs, doctors now commonly use drugs called colony-stimulating factors or growth factors to help the body make its own. These drugs stimulate the body to make neutrophils and other types of granulocytes.
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.
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Last Revised: June 20, 2016
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