Blood transfusion is the transfer of blood or blood components into a person’s bloodstream. People who lose large amounts of blood in accidents or surgery often need blood transfusions. Others have them to increase an inadequate number of blood cells or to provide substances lacking in their blood. Transfusion is a safe, effective medical procedure that saves many lives.
Blood banks collect, store, and distribute the blood for transfusion. Donors provide the blood. Blood banks in the United States follow guidelines set by the Food and Drug Administration (FDA). The American Red Cross collects more than 6 million units of blood each year, about half the blood collected in the United States. One unit of blood contains 450 milliliters (15 ounces) of blood plus 63 milliliters (2 ounces) of a preservative solution. See Red Cross (The American Red Cross) .
Blood contains red blood cells, white blood cells, and platelets. Red blood cells carry oxygen and remove carbon dioxide from the body’s tissues. White blood cells fight infections. Platelets are tiny cells that help form blood clots, which control bleeding. A yellow-brown liquid called plasma surrounds the red blood cells, white blood cells, and platelets. Plasma contains hundreds of dissolved substances, including proteins that enable blood to clot and others that fight infections.
Most people need only some parts of blood in a transfusion. For example, in a disease called hemophilia, blood does not clot normally. A person with hemophilia can receive a transfusion of clotting factors, the plasma proteins that cause blood to clot. Another person can receive a transfusion of red blood cells from the same unit of blood.
How blood is collected.
Donors must meet strict health requirements before giving blood. Blood banks test donors for normal blood pressure, body temperature, and pulse. Blood banks also ask donors about illness, foreign travel, or other factors that might indicate unsafe blood. Donors must be at least 17 years old and weigh 110 pounds (50 kilograms). A person can usually donate a unit of blood every two months.
During collection, a health-care worker takes blood from a vein in the donor’s arm. Some blood samples are sent to a laboratory for tests. The remaining blood is transferred to a bag that contains a preserving solution of citrate and nutrient sugar. A machine called a blood cell separator breaks up the blood into its parts.
Laboratory technicians classify the blood samples into one of four ABO types and as Rh positive or Rh negative (see Blood (Blood groups) ). They then carefully label all parts of the same unit of blood. Technicians also test the blood samples for certain infections, including the AIDS virus and a liver infection called hepatitis B. If the samples carry such infections, all blood collected from the donor is discarded.
Large numbers of platelets can be obtained from a single donor by a technique called plateletpheresis << PLAYT liht fuh REE sihs >> . In plateletpheresis, a health-care worker places a needle in each arm of the donor. Blood from one needle flows to a blood cell separator, which removes the platelets. The remaining components return to the donor through the other needle. A person can donate platelets every 48 hours—up to 24 times in a year—because the body rapidly replaces them. Blood banks can store platelets for five days at room temperature.
Types of transfusion.
Three important types of blood transfusions are (1) red blood cell (RBC) transfusion, (2) platelet transfusion, and (3) clotting factor transfusion. Some people also need transfusions of whole blood or white blood cells.
RBC transfusion is the most common type of transfusion. It helps people who lose large amounts of blood in accidents or surgery. Before an RBC transfusion, samples of the patient’s and the donor’s blood are mixed to check for a harmful reaction. This test is called a cross-match. During the transfusion, a tube carries red blood cells to a vein in the patient’s arm. A special filter in the tube removes clumps, which may be fatal if they reach the patient’s body. Blood banks can refrigerate red blood cells for 35 to 42 days or freeze them for years.
People who lose large amounts of platelets because of infection or the action of certain drugs may need a platelet transfusion. Plateletpheresis makes it possible to obtain enough platelets for a transfusion from a single donor. The use of platelets from one donor reduces the chance of a harmful reaction to the transfused platelets.
A clotting factor transfusion is lifesaving for people whose blood does not clot normally. One source of clotting factors is frozen plasma. Blood banks freeze plasma soon after collection and thaw it before a transfusion. The solid substance that remains in the bag after thawing, called cryoprecipitate, contains the clotting factors. The clotting factors are injected into a vein in the patient’s arm. Clotting factors can be obtained from frozen plasma for up to one year.
Risks of transfusion.
There is little health risk involved in donating blood. However, possible complications for the recipient of a transfusion range from mild to serious. Mild complications might include a fever or an allergic reaction, such as a rash or wheezing. Serious complications might include dangerous illness or death. For example, an acute hemolytic transfusion reaction may occur if a patient mistakenly receives red blood cells of the wrong type. The patient’s blood quickly destroys the red blood cells. The reaction may involve chills, fever, chest and back pain, abnormal bleeding, kidney failure, or even death.
Careful testing can prevent many serious complications from blood transfusions. Today, the risk of catching an infectious disease from a transfusion is small because blood is tested for many diseases. Since 1985, when laboratories began checking all donated blood for the HIV virus, AIDS cases from transfusions have dropped dramatically (see AIDS (Diagnosis) ; Hemophilia (Treatment) ).
The risks of transfusions—which are small but serious—have caused scientists to search for safer options. Some people store their own blood in case they need a transfusion. Scientists are also investigating artificial blood substitutes, which would not be perishable or carry disease.
History.
In 1667, French physician Jean-Baptiste Denis performed the first known blood transfusion to human beings. He injected lamb’s blood into three patients, but one died soon after. Interest in blood transfusion declined until 1829, when British obstetrician James Blundell successfully used transfusions on women in childbirth. The discovery of blood types in the early 1900’s by Austrian-American immunologist Karl Landsteiner increased the safety of transfusion. After World War II (1939-1945), blood transfusion became a common treatment for many illnesses and medical emergencies.
The AABB (formerly the American Association of Blood Banks) is an association of hospital and community blood banks and their personnel. In addition to inspecting and accrediting blood banks, they publish informational material on blood banking, blood transfusion, and careers in blood banking. The association has headquarters in Bethesda, Maryland.
