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Children's Hospital of San Antonio (Christus Health)

Children's Hospital of San Antonio

333 N. Santa Rosa St.
San Antonio, TX 78207
(210) 704-2011

Blood Transfusions

What Is a Blood Transfusion?

A blood transfusion is when a donor's blood is transferred to a patient. The blood is transferred into the patient's body through a vein. A blood transfusion can make up for the loss of blood

Blood transfusions save lives every day. Hospitals use them to help people who are injured, having surgery, getting cancer treatments, or being treated for other diseases that affect the blood, like sickle cell anemia.

A Bit About Blood

As blood moves throughout the body, it carries oxygen and nutrients to all the places they're needed. Blood also collects waste products, like carbon dioxide, and takes them to the organs responsible for making sure wastes leave the body.

Blood is a mixture of cells and liquid, and each part has a specific job:

  • Red blood cells carry oxygen to the body's tissues and remove carbon dioxide. These cells are the ones that are most commonly transfused.
  • White blood cells help the body fight infection by making antibodies, (proteins that help destroy germs in the body).
  • Platelets, the smallest blood cells, help blood clot and control bleeding.
  • Plasma, the pale yellow liquid part of whole blood, is a mixture of water, proteins, electrolytes, carbohydrates, cholesterol, hormones, and vitamins.

Blood cells are made in the bone marrow (a spongy material inside many of the bones in the body). A full-grown adult has about 10 pints of blood (almost 5 liters) in their body.

What Are Blood Types?

Blood from a donor needs to match the blood type of the person receiving it. There are eight main blood types:

  1. O positive
  2. O negative
  3. A positive
  4. A negative
  5. B positive
  6. B negative
  7. AB positive
  8. AB negative

In emergencies, there are exceptions to the rule that the donor's blood type must match the recipient's exactly. Blood type O negative is the only type of blood that people of all other blood types can receive. Medical teams use it in situations when patients need a transfusion but their blood type is unknown. Because of this, O negative donors are called "universal donors." People who have type AB blood are called "universal recipients" because they can safely receive any type of blood.

A blood transfusion usually isn't whole blood — it could be any one of the blood's components. For example, chemotherapy can affect how bone marrow makes new blood cells. So some people getting treatment for cancer might need a transfusion of red blood cells or platelets.

Other people might need plasma or only certain parts of plasma. People who have hemophilia, a disease that affects the blood's ability to clot, need plasma or the clotting factors contained in plasma to help their blood clot and prevent internal bleeding.

Where Does the Blood Come From?

Because there's no substitute for blood, the blood supply used for transfusion must be donated. The three types of blood donation are:

Autologous (pronouced: ah-TOL-uh-gus) blood donation. This is when someone donates their own blood ahead of time for a planned surgery or other procedure.

Directed donation. This is when a family member or friend with a compatible (good fit) blood type donates blood specifically for use by a patient in need of transfusion.

Volunteer donation. There's no medical proof that blood from directed donors is any safer than blood from volunteer donors. So most patients receive blood donated through blood drives. These are often run by agencies like the American Red Cross. The minimum age for donating blood is 16 or 17 years old, depending on where a person lives.

What Happens During a Blood Transfusion?

When someone gets a transfusion:

  • Blood is given through a needle placed in a vein.
  • The needle is attached to thin plastic tubing that connects to a plastic bag containing the blood.
  • The vital signs (temperature, blood pressure, and heart rate) are checked before, during, and after the transfusion.
  • A nurse watches for any signs of an allergic or other type of reaction, including rash, fever, headache, or swelling.

Transfusions usually take 1 to 4 hours, depending on how much blood is given and the person's blood type. Someone getting a transfusion can sit comfortably in a reclining chair or lie down on a bed, watch a movie, listen to music, or play quietly, and might be able to eat and drink, walk around a bit, and use the bathroom.

After the transfusion, the plastic tube is removed from the vein and a bandage is placed over the area. The site may be slightly sore or tingly for a little while. Medicine may be given for any mild side effects, such as fever or headache.

Are There Any Risks to Blood Transfusions?

Some people worry about getting diseases from infected blood, but the United States has one of the safest blood supplies in the world. Many organizations, including community blood banks and the federal government, work hard to ensure that the blood supply is safe.

All blood donors must give a detailed history, including recent travel, infections, medicines, and health problems. In addition, the American Red Cross and other donation groups test donated blood for viruses like HIV (the virus that causes AIDS), hepatitis B, hepatitis C, syphilis, and West Nile virus. Since blood can also be infected with bacteria or parasites, some blood components also get tested for these. If any of these things are found, the blood is destroyed.

Also, the needles and other equipment used are sterile, and are used only on one person and then thrown away in special containers.

What Are the Benefits of Blood Transfusions?

In people with anemia or those getting chemotherapy, the greatest benefit of a transfusion is increased blood flow to nourish the organs and improve oxygen levels in the body. This can keep them from feeling too tired and help give them enough energy for the activities of daily life. Benefits like this often are felt fairly quickly.

For patients with bleeding problems, transfusions with platelets or plasma can help to control or prevent bleeding problems.

The Red Cross estimates that 15% of all blood donors in the United States are high school or college students. If you are eligible and wish to donate blood, contact your local blood bank or the American Red Cross for more information on what's involved. You could help save someone's life.

Reviewed by: Kate M. Cronan, MD
Date reviewed: January 2019