Anemia
Anemia
Anemia means literally “lack of blood.” In fact it is a reduction in the number of red blood cells, plasma, or packed red blood cells to a level that is lower than necessary for normal functioning. This is the result of the inability to replace lost cells or plasma volume at the rate the cells are being lost.
Anemia can result from a rapid loss of blood cells as occurs after an injury, from a reduced rate of replacement, or from an abnormally rapid destruction of blood cells within the body that outstrips the replacement ability of bone marrow.
Normally the red blood cell count for an adult male is 5.4 million per cubic millimeter (mm) of blood at sea level. The count for the adult female is 4.8 million per cubic mm. An adult male is considered anemic if his red cell count falls below 4.5 million per cubic mm, and the female if her count is less than 4 million per cubic mm. The normal rate of replacement for red blood cells is 40,000 to 50,000 new cells per cubic mm per day. Blood cells are generated within the bone marrow.
Any time the integrity of the body is violated blood can be lost. An automobile accident, a wound, a fall, or surgical procedure can produce copious blood loss. A trauma or wound that opens a major blood vessel allows blood to be pumped from the closed circulatory system and depletes the blood volume. Certainly the body is not able to replace such a rapid loss of blood cells or plasma.
Surgical procedures have become more refined, such that they cause little loss of blood. Refinements in techniques, as well as in instrumentation, have rendered modern surgical procedures blood-conserving transactions.
A great deal of surgery is carried out using flexible scopes and instruments that can be inserted into the body through very small incisions. The surgical procedure is carried out by the physician who can see the surgical field by means of a miniature camera on the tip of the instrument. Long incisions followed by clamping of bleeding arteries and veins have been replaced. The need for blood transfusions during surgery has been reduced markedly over the past decade. A patient who may need blood replacement is urged to have his own blood collected prior to surgery, so there will be no subsequent problems from the transfusion.
Anemia can result from non-surgical causes. The best-known example is the anemia that can occur in an expectant mother. This form of anemia affects up to 20% of woman of childbearing age in the United States. The resulting physical and mental fatigue can be mistaken for the consequences of daily life, and the anemia can go undiagnosed. This can be problematic for the fetus, causing curtailed growth and even death.
A deficiency in red blood cell production is the most common cause of anemia, and a lack of iron is the most common reason for low cell production. Iron is the basic atom of hemoglobin, the substance that gives blood its red color and is responsible for carrying oxygen and carbon dioxide through the body. The normal level of iron in the body is 0.1-0.2 oz (3-5 g), depending upon gender and body size.
Iron deficiency occurs as the result of inadequate intake of iron, loss of iron in young women of child-bearing age through menstruation and childbearing, impaired absorption of iron, which may occur following removal of part of the stomach and small intestine, or because of a chronic loss of low volumes of blood within the digestive system through polyps, cancer, or ulcerations brought on by excessive aspirin intake.
Old and nonfunctional red blood cells are culled from the blood stream by the spleen. The cells are destroyed and the iron molecule within the hemoglobin is transferred back to the bone marrow for reuse, a classic example of recycling. Red blood cells that escape the body, however, take iron with them. Of the usual iron intake of 10-20 mg daily in the diet, about one or two mg is absorbed to replace lost iron. Absorption is increased in women who are menstruating or are pregnant.
People with iron deficiency anemia will have abnormally small red blood cells and low hemoglobin levels even though the total red blood cell count may be normal. Supplementary iron intake may resolve the problem, but surgery may be necessary if the underlying cause is a polyp or other area bleeding internally.
Aplastic anemia is a life-threatening form of anemia resulting from insufficient production of blood cells. The underlying cause of the disease is in the bone marrow itself. Aplastic anemia can be brought about by exposure to toxic chemicals or radiation or by excessive intake of certain medications. Removal of the toxic agent or getting away from the source of radiation usually will allow the patient to recover without further events. However, a form of aplastic anemia known as idiopathic, which means a disease of unknown cause, may well result in death.
Aplastic anemia affects all cells in the blood, including the white blood cells and blood platelets. Loss of white blood cells, the core of the immune system, leaves one susceptible to infection. Loss of blood platelets, which are necessary to the clotting process, means bleeding into the skin, digestive system, urine, or nervous system may occur, as may repeated nosebleeds.
Treatment for this form of anemia is to remove the agent causing it, if known, and to provide supportive treatment until the bone marrow recovers. In extreme cases, bone marrow transplantation from a compatible individual may be attempted and is sometimes successful.
Another form of anemia is called megaloblastic anemia. Megaloblastic refers to the large, immature blood cells seen with this kind of anemia. One form, called pernicious anemia, is the result of a digestive inadequacy in which vitamin B12 is not absorbed through the intestine. The condition also is caused by a parasitic infection, as with a tapeworm, certain digestive diseases, cancer, anti-cancer chemotherapeutic agents, and most commonly by lack of folate. It is an anemia often seen in elderly people who suffer from malnutrition, alcoholics, teenagers (possibly also related to malnutrition), and pregnant women.
This form of anemia may be corrected easily by placing the individual on a balanced, adequate diet or by replacing lowered levels of folate or vitamins.
KEY TERMS
Bone marrow— A spongy tissue located in the hollow centers of certain bones, such as the skull and hip bones. Bone marrow is the site of blood cell generation.
Hemolytic anemia— Hemolytic means destruction of the blood cell, an abnormal rate of which may lead to lowered levels of these cells.
Menstruation— The normal, nearly monthly bleeding cycle experienced by women of childbearing age. It is the result of lack of a fertilized egg that triggers the loss of the lining of the uterus (womb) and subsequent bleeding.
Spleen— An organ lying just under the diaphragm in the abdomen that removes old or damaged blood cells from circulation. The spleen is not a critical organ and can be removed if necessary.
A well-known form of anemia is sickle cell anemia. Although blood cell levels are not lowered in sickle cell anemia, the blood cells may be nonfunctional at times, resulting in oxygen starvation of some body tissues.
Other types of anemia are rare. These include a form called spherocytosis, which results in a spherical form of red blood cells resulting from an abnormality in the cell membrane; a similar form called elliptocytosis; and others resulting from decreased or abnormal hemoglobin production.
Resources
BOOKS
Gomez, Joan. Anemia in Women: Self-Help and Treatment. Alameda, CA: Hunter House Publishers, 2002.
Wailoo, Keith. Dying in the City of the Blues: Sickle Cell Anemia and the Politics of Race and Health. Chapel Hill, NC: University of North Carolina Press, 2001.
Williams, Shawn M. Danielle’s Story: A Daughter’s Battle with Aplastic Anemia. Bloomington, IN: Authorhouse, 2006.
Larry Blaser