Blood Transfusion

Blood transfusion is a procedure in which a patient receives a blood product (part of another person's donated blood) through an intravenous line.

Blood transfusions are very common. Each year, about 5 million Americans receive a blood transfusion. The procedure usually takes one to four hours, depending on how much blood is needed.

Why Blood Transfusion Is Done

The heart pumps blood through a network of arteries and veins throughout the body, the circulatory system. Blood has many vital jobs. It carries oxygen and other nutrients to the body's organs and tissues and transfers waste products to areas where they can be excreted. Blood transfusions are done to replace blood lost during surgery or a serious injury. They are also done if the patient's body is not making blood properly because of an illness.

Typical situations in which blood products are given include:

• Major injuries after an accident or disaster.
• Surgery on an organ prone to bleeding, such as the liver or the heart. About one-third of all heart surgery patients have a transfusion.
• Any surgical procedure where unexpected blood loss may occur.
• A severe infection or liver disease that stops the body from properly making blood or some parts of blood.
• Severe anemia. Illnesses that cause anemia include kidney disease or cancer. Medicines or radiation used to treat a medical condition also can cause anemia. There are many different types of anemia, including aplastic, Fanconi, hemolytic, iron-deficiency, and sickle cell anemias, as well as thalassemia.
• Bleeding in the context of a bleeding disorder, such as hemophilia or thrombocytopenia.

Types

An electron microscopic image of blood showing red cells (large, dimpled disks) and platelets (small disks in background and foreground). Source: National Cancer Institute via Wikimedia Commons.

Contrary to popular belief, "whole blood," or blood drawn directly from a vein, is rarely given. Instead, donors' blood, after being screened for infection, is processed into several separate "blood products." This is safer and more efficient. These blood products include:

Packed red blood cells (pRBCs)

Packed red blood cells are what most people think of when they imagine a blood transfusion—the plastic bag of bright-red liquid hanging from an IV pole. This is the most common type of transfusion.

• Red blood cells (RBCs) are the part of the blood that carry oxygen to the rest of the body. They also help the body get rid of carbon dioxide and other waste products. RBCs provide oxygen-carrying capacity; an analogy is to think of them as trucks shipping oxygen. RBCs are filled with an iron-rich protein called hemoglobin], which can be thought of as containers on the truck that carry the oxygen.
• A normal hemoglobin level in an adult male is about 12 to 18 grams per deciliter (g/dL). A single unit of packed red cells will raise increase the hemoglobin level 1 g/dL. For example, a trauma victim requiring four units of pRBCs will raise his hemoglobin from 6 g/dL to 10 g/dL (unless he bleeds as fast as he's transfused).
• A unit of pRBCs amounts to 250 milliliters (mL), or about one cup. The trauma victim above would have received a liter of blood products.
• Packed red blood cells can be processed in two ways: they can be washed, or cleansed of almost all traces of other blood products; or they can be leukocyte-poor, which means they've been filtered of all white blood cells. People with certain illnesses require these specialized products.

Fresh frozen plasma (FFP)

Plasma is the liquid component of blood. It's mainly water, but also contains proteins, clotting factors, hormones, vitamins, cholesterol, sugar, sodium, potassium, calcium, and more. It has proteins called clotting factors, which allow the blood to clot. Fresh frozen plasma is given to people with disorders causing deficiencies of clotting factors to prevent them from dangerous bleeding. The liver ordinarily produces clotting factors, so people with liver disease are often the ones who need FFP. Another common reason a person needs FFP is if he or she has taken too much of the blood-thinner warfarin (Coumadin) and is bleeding or about to have surgery.

• It is called fresh frozen plasma because the plasma is separated from the rest of the blood and frozen at -18°C within 8 hours. Once thawed it must be used within 24 hours.
• A unit of FFP amounts to 175 to 250 mL, or less than a cup. Typically, two to four units are given at a time.
• The effects of FFP are only temporary, lasting about 12-24 hours, so if bleeding is ongoing or the liver is not functioning, the transfusion often needs to be repeated.

Cryoprecipitate

Cryoprecipitate is a portion of plasma that contains certain specific clotting factors, including Factor VIII (the factor that is missing in patients with hemophilia A) and fibrinogen. Hemophilia is a rare, inherited bleeding disorder in which the blood does not clot normally. People with hemophilia will bleed for a longer period of time than others after an injury or accident. They may also bleed internally, especially in the joints (knees, ankles, and elbows).

Other common reasons to give cryoprecipitate include disseminated intravascular coagulation, cardiothoracic surgery, or obstetric emergencies like placental abruption or HELLP syndrome.

Platelets

A bag of platelets, ready to be transfused. Source: Wikimedia Commons

Platelets, or thrombocytes, are tiny cell structures necessary in the blood clotting process. Patients may develop platelet deficiencies, called thrombocytopenia, which increases their risk of bleeding.

• The normal number of platelets ranges from 150,000 to 450,000 per microliter.
• The risk of bleeding begins to increase when the platelet number falls below 50,000, and becomes very high when it is below 10,000.
• A unit of platelets will raise platelet levels by about 10,000.
• Platelets are commonly given several units at a time, in 4-packs or 6-packs, to raise a low platelet count by 40,000 to 60,000.

Other blood products

There are many other ways to process blood. The resulting products include granulocytes (white cells), immunoglobulin, irradiated products, and stem cells.

Preparation

A diagram of a centrifuged tube of blood. Source: Wikimedia Commons

Blood products are harvested from the donor when the donor gives blood.

The blood is spun down in a centrifuge, a machine which rapidly spins the blood until the various parts of the blood separate. The heavier parts like RBCs (erythrocytes) sink to the bottom of the tube, plasma stays at the top of the tube, and between them is the buffy coat, which is full of platelets (thrombocytes) and white cells (leukocytes).

Blood types

Blood types and their compatibility. O can be given to anyone but can only receive O. AB can receive any type but can only be given to AB. Source: Wikimedia Commons

Each person has one of the following blood types: A, B, AB, or O. Also, every person's blood is either Rh-positive or Rh-negative. So, for example, type A blood is either "A positive" or "A negative."

The blood used in a transfusion must be compatible with the patient's blood type because antibodies (proteins) in the patient's blood will attack the newly transfused blood cells. This may cause a severe reaction or even death. Thorough testing of the donor's and the recipient's blood is performed to check the compatibility status.

Type O blood is called the universal donor because it safe for nearly everyone. About 40% of the population has type O blood. Type O negative blood is usually reserved and used for emergencies when the patient may be bleeding profusely and there is no time to test a person's blood type.^[1]

People with type AB blood are called universal recipients. This means they can get any type of blood. AB donors can only safely donate to other people with AB blood, though.

People with Rh-positive blood can get Rh-positive or Rh-negative blood. But people with Rh-negative blood should get only Rh-negative blood. Rh-negative blood is used for emergencies when there's no time to test a person's Rh type.

Uncommonly, a patient may have antibodies to blood of their own type, and donor blood products need special additional screening before they can be effectively given. This can be a problem as it may delay blood transfusion in urgent situations.

Blood Banks

Blood banks collect, test, and store blood. They screen each blood unit to find out the blood type (A, B, AB, or O) and whether it is Rh-positive or Rh-negative. Again, someone receiving an incompatible unit may experience severe reactions.

Many patients who still feel uncomfortable receiving blood donated from someone they do not know, an anonymous donor, have the option of donating blood to be used for their own use at a later date. If a patient is going to have surgery, they may need a blood transfusion because of blood loss during the operation. If it is surgery that is scheduled months in advance, patients may be able to donate their own blood and have it stored. It can then be used when they need blood during surgery. This is called an autologous transfusion.

Preparation

Before a blood transfusion, a technician tests the patient's blood to find out what blood type they have (that is, A, B, AB, or O and Rh positive or Rh negative). The blood type used in the transfusion must be compatible with the patient's blood type. If it is not, antibodies (proteins) in the patient's blood will attack the new blood and a severe reaction can occur.

Some patients have allergic reactions even when the blood given does work with their own blood type. To prevent this, the doctor may prescribe a medicine to stop allergic reactions.

Most patients do not need to change their diet or activities before or after a blood transfusion.

How Blood Transfusion Is Done

Blood transfusions take place in either a doctor's office or a hospital. They can be done at the patient's home, but this is less common.

A needle is used to insert an intravenous (IV) line into a blood vessel. Through this line, the blood is transfused. The procedure usually takes one to four hours. The time depends on how much blood is needed, which blood product is given, and whether the patient's body can safely receive blood quickly or not.

During the blood transfusion, a nurse carefully watches the patient, especially for the first 15 minutes. This is when bad reactions are most likely to occur.

After a blood transfusion, vital signs are checked (such as temperature, blood pressure, and heart rate).

Follow-up blood tests may be necessary to show how the body is reacting to the transfusion.

Benefits

Blood transfusions are only given if the benefits outweigh the risk in each specific situation, but the number of patients who get sick or die from not getting blood is far higher than the number who are harmed by the blood. Patients who don't have enough blood, either from anemia or bleeding, need the extra oxygen-carrying capacity that blood provides and will almost always benefit from receiving blood.

Risks

Most blood transfusions go very smoothly. However, mild problems and, rarely, serious problems can occur.

Safety of the blood supply

Because transfusing blood has the potential to spread disease from donor to recipient, the blood supply is very carefully screened. In the US, the Food and Drug Administration (FDA) is responsible for the safety of blood products.

People interested in donating blood are interviewed about their personal history, including their health and past travel, risk of or past history of infectious diseases. For example, if there is a history of infectious hepatitis, donation is generally not allowed. In the US, these people would be placed on a list to prevent inadvertent future use of their blood.^[2]

Blood can be washed, irradiated, or spun down further before it is ready to be given. Some blood banks remove white blood cells; this process is called white cell or leukocyte reduction. Some patients are allergic to white blood cells in donated blood, so removal of these cells decreases the likelihood of allergic reactions.

Donated blood is screened for seven different infectious agents:

• Hepatitis B
• Hepatitis C
• Human immunodeficiency virus (HIV) types 1 and 2
• Human T-lymphotropic virus, types I and II
• Syphilis

There is still a small chance of contracting an infectious disease from blood transfusions, but blood donations are considered very safe for transfusion. If a person needs blood, then the risk of the blood itself being harmful are much lower than the risk of not receiving the blood.

Allergic reaction

Some people have allergic reactions to the blood given during transfusions. This can happen even when the blood given is the right blood type.

Allergic reactions can be mild or severe. Symptoms can include:

• Anxiety
• Chest and/or back pain
• Trouble breathing
• Fever, chills, flushing, and clammy skin
• A high pulse or low blood pressure
• Nausea (feeling sick to the stomach)

A transfusion is stopped at the first signs of an allergic reaction. The health care team determines how mild or severe the reaction is, what treatments are needed, and if the transfusion can safely be restarted.

Viruses and infectious diseases

Some infectious agents, such as HIV, could survive in the donated blood and be transmitted to the person receiving the blood transfusion. To keep blood as safe as possible, blood banks thoroughly screen donated blood. So, although there is a risk of catching an infectious disease from a blood transfusion, there is a small risk.

• HIV. The risk of getting HIV from a blood transfusion is lower than the risk of getting killed by lightning. Only about 1 in 2 million donations may carry HIV and transmit HIV if given to a patient. HIV is screened for in all units of blood in the US.
• Hepatitis B and C. The risk of having a donation that carries hepatitis B is about 1 in 205,000. The risk for hepatitis C is 1 in 2 million. If a patient receives blood that contains hepatitis, they will likely develop the virus. Hepatitis B and C are screened for in all units of blood in the US.
• Variant Creutzfeldt-Jakob disease (vCJD). Variant CJD is the human version of mad cow disease. It is a very rare, fatal brain disorder. There is a possible risk of getting vCJD from a blood transfusion, although the risk is extremely low. Still, people who may have been exposed to vCJD aren't eligible blood donors. For example, anyone who spent more than six months in the United Kingdom during the years 1980-1996 are, at present, automatically ineligible to donate blood. Go to the AABB Web site for more information about vCJD.

Fever

A patient may get a sudden fever during or within a day of the blood transfusion. This is usually the body's normal response to white blood cells in the donated blood and is called a benign febrile nonhemolytic transfusion reaction (FNHTR). Over-the-counter fever medicine will usually treat the fever.

Unfortunately, fevers can also mean that a more dangerous reaction is taking place—for example, a hemolytic reaction. Since it's hard to tell the difference right away, fevers during transfusions require the transfusion to be stopped and blood samples taken to rule out a transfusion reaction. This, in turn, delays care, and the best approach to handling this situation is debated.^[3]

Some blood banks remove white blood cells from whole blood or different parts of the blood. This makes it less likely that the patient will have a reaction after the transfusion.

Lung injury

Transfusion-related acute lung injury (TRALI) is the third most common cause of transfusion-related deaths.^[4] This usually occurs within about six hours of the blood transfusion. Symptoms include fever, dyspnea (feeling of trouble breathing), cough, fast breathing, bluish skin coloration, and low oxygen levels in the blood. Pulmonary edema, or fluid in the lungs, interferes with breathing and oxygen exchange. The diagnosis may be confused with acute respiratory distress syndrome, sepsis, heart failure, or fluid overload. Most TRALI patients recover within 48 hours, although many need to go on a breathing machine (mechanical ventilator) temporarily, and survivors are at risk of getting it again the next time they get blood products. However, in 5-8% of patients, TRALI is fatal.

Researchers aren't sure why blood transfusions damage the lungs. Antibodies (proteins) which are more likely to be found in the plasma of women who have been pregnant multiple times, may disrupt the normal way that lung cells work. Because of this risk, hospitals are starting to use men and women's plasma differently.

Acute hemolytic transfusion reaction

Acute hemolytic transfusion reaction is serious, but rare. It occurs if the blood type given during a transfusion doesn't match or work with the patient's blood type—an administrative mixup is usually to blame.^[5] The body attacks the new red blood cells, causing hemolysis (breakdown of red blood cells) which then produces substances that harm the kidneys.

The symptoms include fever, chills, nausea, pain in the chest or back, and dark urine. The transfusion must be stopped at the first sign of this reaction.

Delayed hemolytic reaction

A delayed hemolytic reaction is a much slower type of reaction. It tends to show up in the second week after the transfusion. The body destroys red blood cells so slowly that the problem can go unnoticed until the red blood cell level is very low.

Both the acute and delayed hemolytic reactions are most common in patients who have had a previous transfusion.

Graft-versus-host disease

Graft-versus-host disease (GVHD) is when white blood cells in the donor's blood attack the patient's tissues. This usually happens in people receiving bone marrow transplants or umbilical cord blood to treat a severely weakened immune system—for instance, in leukemia patients. GVHD ranges from mild to fatal.

Symptoms start within a month of the blood transfusion. They include fever, rash, and diarrhea. Sometimes people have this disease chronically.

Iron overload

Getting many blood transfusions can cause too much iron to build up in the blood (iron overload), termed secondary hemochromatosis. People with a blood disorder like thalassemia, who need multiple transfusions, are at higher risk of iron overload. Iron overload can damage the liver, heart, and other parts of the body.

Patients with iron overload may need iron chelation therapy. For this therapy, medicine is given through an injection or as a pill to remove the extra iron from the body.

Statistics

According to America's Blood Centers:

• More than 4.5 million patients need blood transfusions each year in the U.S. and Canada.
• Each day in the U.S. and Canada, 43,000 pints of donated blood are used.
• About 1 in 7 people entering a hospital need blood.

Alternatives

Researchers are trying to find ways to make blood. There is currently no man-made alternative to human blood. However, researchers have developed medicines that may help do the job of some blood parts.

For example, some patients with kidney problems can now take a medicine called erythropoietin that stimulates their bodies to make more red blood cells. This means they may need fewer blood transfusions.

Surgeons try to reduce the amount of blood lost during surgery so that fewer patients need blood transfusions. Sometimes they can collect and reuse the blood for the patient.

Cultural Considerations

A religious group called the Jehovah's Witnesses teaches that people should not receive blood transfusions. This is because of a passage in the Old Testament that disallows the Jews from consuming blood. In the United States, adult Jehovah's Witnesses who are of sound mind are legally allowed to refuse a blood transfusion, even if that means they will die. They are not permitted to refuse a life-saving transfusion on behalf of a child, however. Some landmark court cases around the world involving Jehovah's Witnesses and blood transfusion are listed here.

Clinical Trials

For a list of clinical trials on blood transfusion, click here.

Related Videos

A haematologist describes the process of giving blood and the reasons why people may need a blood transfusion. She also explains how the blood is tested to reduce the risk of infection.

References

1. ↑ Dutton RP, Shih D, Edelman BB, Hess J, Scalea TM. Safety of uncrossmatched type-O red cells for resuscitation from hemorrhagic shock. J Trauma. 2005 Dec;59(6):1445-9. Abstract
2. ↑ US Food and Drug Administration: Blood
3. ↑ Ezidiegwu CN, Lauenstein KJ, Rosales LG, Kelly KC, Henry JB. Febrile nonhemolytic transfusion reactions. Management by premedication and cost implications in adult patients. Arch Pathol Lab Med. 2004 Sep;128(9):991-5. Abstract | Full Text
4. ↑ Looney MR, Gropper MA, Matthay MA. Transfusion-related acute lung injury: a review. Chest. 2004 Jul;126(1):249-58. Abstract | Full Text
5. ↑ Linden JV. Errors in transfusion medicine. Scope of the problem. Arch Pathol Lab Med. 1999 Jul;123(7):563-5. Abstract | Full Text

External Links

World Health Organization: Blood product safety

American Red Cross

America's Blood Centers: North America's largest network of non-profit, community blood centers.