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Blood transfusion can be life-saving. Blood
products include whole blood (blood with all of its
components, rarely used now), packed red blood cells (blood
cells that carry oxygen), platelets (cells in the
blood that allow blood clots to form), plasma (the
liquid portion of blood without cells), and concentrated clotting factors.
When packed red blood cells are transfused, an individual's blood count
increases. This blood count is usually measured as the hemoglobin level. Hemoglobin is a protein that carries oxygen to the
tissues and cells of the body. Normal hemoglobin levels are about 12 to 15
grams per 100 milliliters of blood for women and about 14 to 17 for men. Although
individual circumstances can be different, anemia (low
red blood cell count) requiring transfusion usually occurs when the hemoglobin
is about 7. Medical research has shown that significant decreases in tissue
oxygen delivery occur when the hemoglobin drops to that level. The October
6, 2004, issue of JAMA includes an article about
blood transfusion in the setting of acute coronary syndrome (heart attack).
Reasons for blood transfusion
Blood loss from injuries or internal bleeding
Blood loss during and after surgery, including
Treatment for leukemia and other types of cancers
Anemia caused by illnesses
Main risks of transfusion
Transfusion reactions from incompatible
bloodEach person has a specific blood type, characterized by the ABO
blood groups and the presence or absence of the Rh factor (Rh positive or
Rh negative). Because reactions can occur if a person receives a transfusion
of improper blood type, a system of checks and balances (known as typing and crossmatching) and other safety procedures have been developed
to prevent transfusion reactions. Such reactions vary from mild (fever or
chills) to severe, such as ABO blood type incompatibility, which can be fatal.
Transmission of an infectious
diseaseBecause of the risk of infections from blood or blood products,
each unit of donated blood is carefully tested for the presence of viruses
(including hepatitis viruses, the human immunodeficiency virus [HIV], cytomegalovirus,
and West Nile virus) and the organism that causes syphilis. With this extensive
testing, the chance of receiving a unit of blood containing the human immunodeficiency
virus is now less than 1 in 1.9 million, and the risk of exposure to the hepatitis
C virus is less than 1 in 1 million. Health history questions of the prospective
blood donor may exclude that person from donating blood, thereby increasing
the safety of donated blood.
For more information
National Heart, Lung, and Blood Institutehttp://www.nhlbi.nih.gov
American Association of Blood Banks http://www.aabb.org
American Red Cross 202/303-4498 http://www.redcross.org
To find this and previous JAMA Patient Pages, go to the Patient Page
link on JAMA's Web site at http://www.jama.com. Many are available in English and Spanish. A Patient Page on blood
donation was published in the April 17, 2002, issue.
Sources: National Heart, Lung, and Blood Institute; American Association
of Blood Banks; American Red Cross
The JAMA Patient Page is a public service of JAMA. The information and recommendations appearing on this page
are appropriate in most instances, but they are not a substitute for medical
diagnosis. For specific information concerning your personal medical condition, JAMA suggests that you consult your physician. This page
may be photocopied noncommercially by physicians and other health care professionals
to share with patients. Any other print or online reproduction is subject
to AMA approval. To purchase bulk reprints, call 718/946-7424.
Torpy JM, Glass TJ, Glass RM. Blood Transfusion. JAMA. 2004;292(13):1646. doi:10.1001/jama.292.13.1646
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