Anemia

18 May

Anemia
Anemia is a reduction in the amount of hemoglobin (the oxygen-carrying protein in red blood cells) or in the number of red blood cells to below normal levels. Anemia reduces the blood’s ability to supply oxygen to the tissues and remove carbon dioxide from the tissues. Anemia can result from excessive bleeding, decreased red blood cell production, or diseases that destroy red blood cells. Symptoms of anemia include paleness, weakness, fatigue, shortness of breath, and palpitations.

Excessive bleeding is the most common cause of anemia. When blood is lost, the body pulls water from the tissues outside the bloodstream in an attempt to

keep the blood vessels filled. This extra water dilutes the blood and reduces the concentration of red blood cells in the blood. The body then increases red blood cell production in an attempt to correct the anemia. Before that occurs, however, the anemia may be so severe that blood pressure falls and the body’s oxygen sup- ply decreases to dangerous levels. Injuries, surgery, or a ruptured blood vessel are examples of possible causes of sudden blood loss that can lead quickly to a heart attack, stroke, or even death.

Chronic (continuous or repeated) internal bleeding is a more common cause of anemia than the sudden loss of blood. Possible causes of chronic internal bleeding include:

•  nosebleeds

•  hemorrhoids

•  ulcers of the stomach or small intestine

•  cancer or polyps in the gastrointestinal tract

•  kidney or bladder tumors

Treatment depends on how rapidly blood is lost and the severity of the ane- mia. Transfusion of red blood cells is the only reliable treatment for rapid blood loss. Locating the source of blood loss and stopping the bleeding are the first steps in treating anemia caused by chronic bleeding. Depending on the cause, this could involve treatment with medication or surgery.

Iron deficiency is one of the most common causes of anemia. An adequate supply of iron is required for red blood cell production. In adults, blood loss is the most common cause of iron deficiency. In men, iron deficiency usually indi- cates bleeding in the gastrointestinal tract. Normal dietary iron intake usually is not enough to replace iron lost from chronic bleeding, since the body has a small iron reserve. Therefore, lost iron must be replaced with supplements. Iron defi- ciency anemia in men is cured by treating the underlying cause.

Anemia also can result from diseases, conditions, and genetic disorders that cause excess destruction of red blood cells, such as sickle-cell disease.

Sickle-Cell Disease

Sickle-cell disease is an inherited disorder characterized by sickle-shaped red blood cells. These cells contain an abnormal form of hemoglobin (the oxygen- carrying protein in red blood cells), which gives them their sickle shape.

Because these deformed blood cells are fragile, they break up as they travel through the blood vessels and have difficulty moving through the capillaries, the tiny blood vessels that deliver oxygen to tissues. The sickle-shaped cells block and damage the capillaries in the spleen, kidneys, liver, brain, bones, and other organs and reduce their oxygen supply. An inadequate supply of oxygen can cause significant damage to organs and tissues.

Sickle-cell disease affects mostly African Americans and people of Mediter- ranean ancestry. A child must inherit the defective gene from both parents to develop the disease. About 10 percent of African Americans have inherited one gene for sickle-cell disease. This means that they have the sickle-cell trait and will not develop the disease but will be carriers who can pass the disease to their children if their partners also are carriers. About 0.3 percent of African Ameri- cans have inherited two genes for sickle-cell disease, and they have the disease.

If you are African American or have a family member with sickle-cell disease and are planning to start a family, talk to your doctor about having a blood test to determine whether you are a carrier of the gene. If you are a carrier, your partner also must be tested. If you are not a carrier, you cannot pass the disease to your children. Both parents must carry the gene to pass the disease to their children.

Symptoms of sickle-cell disease may include headaches, breathlessness on exertion, fatigue, and jaundice (yellowing of the skin and the whites of the eyes). Bouts of severe pain, known as sickle-cell crises, can occur when dead or dam- aged red blood cells collect in the joints or in other parts of the body. A sickle- cell crisis also can result from an infection, dehydration, or prolonged exposure to cold weather. In addition, any activity that reduces the amount of oxygen in the blood, such as vigorous exercise, mountain climbing, or flying at high alti- tudes without sufficient oxygen, may result in a sickle-cell crisis. The crisis is characterized by a sudden worsening of the anemia, pain in the abdomen or long bones, fever, and sometimes shortness of breath. Abdominal pain may be severe and accompanied by nausea and vomiting.

Poor circulation to the skin may lead to sores on the legs, especially at the ankles. Damage to the nervous system may cause strokes. Older men may experience a decline in lung and kidney function. Younger men may develop per- sistent and often painful erections (priapism; see page 177).

Rarely, a person who carries the sickle-cell trait may have blood in the urine caused by bleeding from the kidneys. If a physician knows that this bleeding is related to the sickle-cell trait, exploratory surgery may be avoided.

Doctors usually recognize the combination of anemia, abdominal and bone pain, and nausea in young black men as signs of sickle-cell disease. The diagno- sis usually is confirmed by electrophoresis, a blood test that can detect abnormal hemoglobin and indicate whether the person has the sickle-cell trait or sickle- cell disease.

In the recent past, people with sickle-cell disease were not expected to live into their 20s. Today, however, most live well past age 50. Deaths caused by exer- tion are rare. Because sickle-cell disease cannot be cured, treatment focuses on preventing crises, controlling the anemia, and relieving symptoms. Folic acid (one of the B vitamins) supplements help the body produce red blood cells to replace dead and damaged sickle cells. People with sickle-cell disease need to avoid activities that reduce the oxygen levels in their blood and should seek med-

ical attention promptly, even for minor illnesses, such as a cold or other viral infection. Immunization against infectious diseases, such as pneumonia and influenza (see page 93), and use of antibiotics to fight infection are essential pre- ventive measures for all people who have sickle-cell disease.

A person who is experiencing a sickle-cell crisis requires immediate treat- ment. He or she is usually given large amounts of fluids intravenously to prevent dehydration, antibiotics to treat infection, and painkillers to relieve the extreme pain. Blood transfusions may be given to increase the amount of normal hemo- globin in the blood. Supplemental oxygen also may be given to help provide more oxygen to the tissues.

Medications also are available to reduce the risks associated with a sickle-cell crisis. One such drug is hydroxyurea, which increases the amount of normal hemoglobin in the blood and thereby decreases the number of red blood cells that become sickle-shaped.

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