大象tv

In a blood transfusion, donated blood or parts of blood (also called blood products) are given to another person who is bleeding or who can’t make enough blood cells.

Why do people with cancer need blood transfusions?

Some reasons people with cancer might need blood transfusions are:

• Some cancers cause bleeding inside the body (internal bleeding)
• Blood cancers (like leukemia) can crowd out healthy blood cells in the bone marrow
• People who have had cancer for a while may develop anemia of chronic disease.
• Cancers that affect organs, like the liver and spleen

Some people with cancer might need blood transfusions because of treatment side effects. For example:

• Chemotherapy and radiation
• Bleeding after surgery

Types of blood products

People who give blood usually donate whole blood. Whole blood can be separated into parts called blood products and each part does a separate job. This way, one unit of whole blood can be used to help more than one person. And the person getting a transfusion only gets the part that they need. These blood products or components are:

• Packed red blood cells
• Platelets
• Plasma
• Cryoprecipitate

Whole blood transfusions are usually saved for emergencies such as trauma or surgery where there is severe blood loss that needs to be replaced quickly. 

Packed red blood cell transfusions

Packed red blood cells are prepared by separating the plasma from blood. Plasma makes up most of the liquid in the blood. Sometimes, white blood cells are also removed and what is left is called leukocyte-reduced red blood cells. Leukocyte-reduced RBCs may be used for people who have a higher risk of reacting to a transfusion.

When are red blood cell transfusions used?

Anemia: Low numbers of red blood cells (RBCs) cause anemia. People with anemia may need RBC transfusions because they don’t have enough hemoglobin. Hemoglobin (Hgb) is the protein on red blood cells that carries oxygen throughout the body. Common causes of anemia in people with cancer include:

• Cancer treatments like chemotherapy or radiation kill RBCs
• Blood cancers like leukemia where cancer cells crowd out RBCs
• Some tumors can make it hard for the body to make RBCs
• Low iron or vitamin B12 levels 

A normal hemoglobin level is about 12 to 18 g/dL. An RBC transfusion may be given if hemoglobin is less than 8 g/dL. It will also depend on your symptoms as well as how long it took for the anemia to develop. Anemia from 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. If your hemoglobin level is lower than normal but you’re not dizzy, pale, or short of breath, you may not need a transfusion.

Surgery: Transfusions may be given before, during, or after surgery to make up for blood loss or if someone has low blood counts.

Platelet transfusions

Platelets are pieces of cells in blood that help make clots and stop bleeding.

A unit of whole blood has only a small number of platelets. So, it takes platelets from several units of whole blood to help keep a person from bleeding. A unit (or pack) of platelets is the amount that can be separated from one unit of whole blood.

Platelets don’t have a blood type like red blood cells do, so patients can usually get platelets from any 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 (called pooled platelets).

Platelets can also be collected by apheresis (sometimes called plateletpheresis). The donor is hooked up to a machine that removes their 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 multiple donors. These are called single donor platelets.

When are platelet transfusions used?

People with cancer might need platelet transfusions if their bone marrow is not making enough platelets. This can happen when chemotherapy or other cancer treatments damage the bone marrow, where blood cells are made. It can also happen in certain blood cancers (like leukemias) when cancer cells in the bone marrow crowd out normal blood cells.

A normal platelet count is about 150,000 to 400,000 platelets per microliter (mcL) of blood. When platelet counts are below a certain level (often 20,000/mcL), a person is at risk for dangerous bleeding. Doctors might suggest a platelet transfusion when the platelet count is below this level or even at higher levels if the person 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.

Plasma transfusions

Plasma is the liquid part of blood. It has proteins called clotting factors that help blood clot. Clots help stop bleeding when we’re injured. Plasma has other proteins, such as antibodies, that help fight infection.

After 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 .

When are plasma transfusions given?

Plasma may be given to patients who are bleeding because their blood doesn't clot the way it should. People with cancer might also be given fresh frozen plasma if they have a condition called disseminated intravascular coagulation (DIC). In DIC, all the clotting factors in the body are used up. Signs and symptoms (such as severe bleeding and bruising) and blood tests help the doctor diagnose DIC.

Cryoprecipitate transfusions

Cryoprecipitate (or cryo) is the part of plasma that separates out (precipitates) when plasma is frozen and then thawed. It has some 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 are pooled together for one transfusion.

When are cryoprecipitate transfusions used?

Cryoprecipitate may be given to replace missing blood clotting factors such as:

• Factor VIII (missing in people with hemophilia A)
• Von Willebrand factor (needed to help platelets work)
• Fibrinogen (protein needed to form a clot)

Donating your own blood to use later

Donating your own blood for later use is called autologous donation. Autologous donation is most often done in the weeks before a scheduled surgery that will likely require blood transfusion. Your own blood can then be used during or after the surgery to replace any blood you may have lost.

This is thought to be the safest form of blood transfusion because you’re getting your own blood back. Still, it’s not totally without risk. There’s always the very small chance that bacterial contamination or clerical errors can happen.

People who can’t donate blood for others may still be able to donate blood for themselves.

There are fees for autologous donation that may not be covered by your insurance. Be aware that your health insurance may not fully pay for this. You and your doctors will need to plan so that your blood cell counts go back to normal before your surgery.

Other treatments

Treatments other than blood product transfusions are sometimes used. These treatments don’t replace blood transfusions, but they may decrease the number of transfusions a person needs.

Volume expanders

When a person has lost a lot of fluids, the body can go into shock. This may be treated or prevented by giving fluids into a vein. This can help increase blood going to internal organs. But these fluids don’t carry oxygen or raise the number of blood cells.

Iron

Iron helps the body make hemoglobin (Hgb). Hemoglobin is the protein on red blood cells that carries oxygen throughout the body. Some people with cancer and anemia (low red blood cells) have low iron levels. Giving iron supplements might help increase hemoglobin and reduce the need for blood transfusions. This can be especially helpful for people with chronic anemia.

There are possible problems with taking iron. For example, there is a risk of iron overload. Iron overload can happen when iron levels in the blood get too high. This can damage some organs.

Growth factors

The body naturally makes hormone-like substances called hematopoietic growth factors. These substances cause the bone marrow to make more blood cells. Growth factors can be used to increase red blood cell, white blood cell, or platelet counts.

Growth factors may be used instead of transfusions. But there are some possible problems that may limit their use.

• They often take days or weeks to increase blood counts. So, they may not help people who need to have their blood cell levels raised quickly, such as those who are bleeding.
• Might not work in people with severe bone marrow disease.  Growth factors can’t work if there are not enough blood-producing cells in the bone marrow.
• Might cause certain types of cancer cells to grow more quickly. These types of cancer include lymphocytic leukemia, multiple myeloma, head and neck cancers, breast cancer, cervical cancer, and some kinds of lung cancer cells.
• Usually cost a lot more than transfusions.

Because of these problems, some growth factors are not used in people whose treatment is expected to get rid of their cancer. And when they are used, they are given for as short a time as possible.

Blood substitutes

So far, there is no real substitute for human blood. But researchers are working to develop a liquid that can carry oxygen and replace blood, at least for a short time.

Some products being tested can do some of the work of red blood cells, such as carrying oxygen to tissues, but cannot replace the many other functions of human blood.