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Thursday, June 20, 2019

Sickle Cell Anemia



                       Sickle Cell Anemia

                   

DEFINITION

Sickle cell anemia is an inherited form of anemia — a condition in which there aren't enough healthy red blood cells to carry adequate oxygen throughout your body.
Normally, your red blood cells are flexible and round, moving easily through your blood vessels. In sickle cell anemia, the red blood cells become rigid and sticky and are shaped like sickles or crescent moons. These irregularly shaped cells can get stuck in small blood vessels, which can slow or block blood flow and oxygen to parts of the body.
There's no cure for most people with sickle cell anemia. However, treatments can relieve pain and help prevent further problems associated with sickle cell anemia.



SYMPTOMSour

Signs and symptoms of sickle cell anemia often don't appear until an infant is at least 4 months old and may include:
  • Anemia. Sickle cells are fragile. They break apart easily and die, leaving you without a good supply of red blood cells. Red blood cells usually live for about 120 days before they die and need to be replaced. But sickle cells die after an average of less than 20 days. This results in a lasting shortage of red blood cells (anemia). Without enough red blood cells in circulation, your body can't get the oxygen it needs to feel energized. That's why naemia causes fatigue.
  • Episodes of pain. Periodic episodes of pain, called crises, are a major symptom of sickle cell anemia. Pain develops when sickle-shaped red blood cells block blood flow through tiny blood vessels to your chest, abdomen and joints. Pain can also occur in your bones. The pain may vary in intensity and can last for a few hours to a few weeks. Some people experience only a few episodes of pain. Others experience a dozen or more crises a year. If a crisis is severe enough, you may need to be hospitalized.
  • Hand-foot syndrome. Swollen hands and feet may be the first signs of sickle cell anemia in babies. The swelling is caused by sickle-shaped red blood cells blocking blood flow out of their hands and feet.
  • Frequent infections. Sickle cells can damage your spleen, an organ that fights infection. This may make you more vulnerable to infections. Doctors commonly give infants and children with sickle cell anemia vaccinations and antibiotics to prevent potentially life-threatening infections, such as pneumonia.
  • Delayed growth. Red blood cells provide your body with the oxygen and nutrients you need for growth. A shortage of healthy red blood cells can slow growth in infants and children and delay puberty in teenagers.
  • Vision problems. Some people with sickle cell anemia experience vision problems. Tiny blood vessels that supply your eyes may become plugged with sickle cells. This can damage the retina — the portion of the eye that processes visual images.

CAUSES

Sickle cell anemia is caused by a mutation in the gene that tells your body to make hemoglobin — the red, iron-rich compound that gives blood its red color. Hemoglobin allows red blood cells to carry oxygen from your lungs to all parts of your body. In sickle cell anemia, the abnormal hemoglobin causes red blood cells to become rigid, sticky and misshapen.
The sickle cell gene is passed from generation to generation in a pattern of inheritance called autosomal recessive inheritance. This means that both the mother and the father must pass on the defective form of the gene for a child to be affected.
If only one parent passes the sickle cell gene to the child, that child will have the sickle cell trait. With one normal hemoglobin gene and one defective form of the gene, people with the sickle cell trait make both normal hemoglobin and sickle cell hemoglobin. Their blood may contain some sickle cells, but they generally don't experience symptoms. However, they are carriers of the disease, which means they can pass the defective gene on to their children.
With each pregnancy, two people with sickle cell traits have:
  • A 25 percent chance of having an unaffected child with normal hemoglobin
  • A 50 percent chance of having a child who also is a carrier
  • A 25 percent chance of having a child with sickle cell anemia

RISK FACTORS

The risk of inheriting sickle cell anemia comes down to genetics. For a baby to be born with sickle cell anemia, both parents must carry a sickle cell gene.
The gene is more common in families that come from Africa, India, Mediterranean countries, Saudi Arabia, the Caribbean islands, and South and Central America. In the United States, it most commonly affects blacks.

COMPLICATIONS

Sickle cell anemia can lead to a host of complications, including:
  • Stroke. A stroke can occur if sickle cells block blood flow to an area of your brain. Signs of stroke include seizures, weakness or numbness of your arms and legs, sudden speech difficulties, and loss of consciousness. If your baby or child has any of these signs and symptoms, seek medical treatment immediately. A stroke can be fatal.
  • Acute chest syndrome. This life-threatening complication of sickle cell anemia causes chest pain, fever and difficulty breathing. Acute chest syndrome can be caused by a lung infection or by sickle cells blocking blood vessels in your lungs. It may require emergency medical treatment with antibiotics and other treatments.
  • Pulmonary hypertension. People with sickle cell anemia can also develop high blood pressure in their lungs (pulmonary hypertension). This complication usually affects adults rather than children. Shortness of breath and fatigue are common symptoms of this condition, which can be fatal.
  • Organ damage. Sickle cells can block blood flow through blood vessels, immediately depriving an organ of blood and oxygen. In sickle cell anemia, blood is also chronically low on oxygen. Chronic deprivation of oxygen-rich blood can damage nerves and organs in your body, including your kidneys, liver and spleen. Organ damage can be fatal.
  • Blindness. Tiny blood vessels that supply your eyes can get blocked by sickle cells. Over time, this can damage the portion of the eye that processes visual images (retina) and lead to blindness.
  • Skin ulcers. Sickle cell anemia can cause open sores, called ulcers, on your legs.
  • Gallstones. The breakdown of red blood cells produces a substance called bilirubin. A high level of bilirubin in your body can lead to gallstones.
  • Priapisum. Men with sickle cell anemia may experience painful, long-lasting erections, a condition called priapism. As occurs in other parts of the body, sickle cells can block the blood vessels in the penis. This can damage the penis and eventually lead to impotence.

TESTS AND DIAGNOSIS

A blood test can check for hemoglobin S — the defective form of hemoglobin that underlies sickle cell anemia. In the United States, this blood test is part of routine newborn screening done at the hospital. But older children and adults can be tested, too.
In adults, a blood sample is drawn from a vein in the arm. In young children and babies, the blood sample is usually collected from a finger or heel. The sample is then sent to a laboratory, where it's screened for hemoglobin S.
If the screening test is negative, there is no sickle cell gene present. If the screening test is positive, further tests will be done to determine whether one or two sickle cell genes are present. People who have one gene — sickle cell trait — have a fairly small percentage of hemoglobin S. People with two genes — sickle cell anemia— have a much larger percentage of the defective hemoglobin.

Additional tests

To confirm any diagnosis, a sample of blood is examined under a microscope to check for large numbers of sickle cells — a marker of the disease. If you or your child has the disease, a blood test to check for anemia — a low red blood cell count — will be done. And your doctor may suggest additional tests to check for possible complications of the disease.
If you or your child carries the sickle cell gene, you may be referred to a genetic counselor — an expert in genetic diseases.

Tests to detect sickle cell genes before birth

Sickle cell disease can be diagnosed in an unborn baby by sampling some of the fluid surrounding the baby in the mother's womb (amniotic fluid) to look for the sickle cell gene. If you or your partner has been diagnosed with sickle cell anemia or sickle cell trait, ask your doctor about whether you should consider this screening. Ask for a referral to a genetic counselor who can help you understand the risk to your baby.

TREATMENTS AND DRUGS

Bone marrow transplant offers the only potential cure for sickle cell anemia. But finding a donor is difficult and the procedure has serious risks associated with it, including death.
As a result, treatment for sickle cell anemia is usually aimed at avoiding crises, relieving symptoms and preventing complications. If you have sickle cell anemia, you'll need to make regular visits to your doctor to check your red blood cell count and monitor your health. Treatments may include medications to reduce pain and prevent complications, blood transfusions and supplemental oxygen, as well as a bone marrow transplant.

Medications

Medications used to treat sickle cell anemia include:
  • Antibiotics. Children with sickle cell anemia may begin taking the antibiotic penicillin when they're about 2 months of age and continue taking it until they're at least 5 years old. Doing so helps prevent infections, such as pneumonia, which can be life-threatening to an infant or child with sickle cell anemia. Antibiotics may also help adults with sickle cell anemia fight certain infections.
  • Pain-relieving medications. To relieve pain during a sickle crisis, your doctor may advise over-the-counter pain relievers and application of heat to the affected area. You may also need stronger prescription pain medication.
  • Hydroxyurea (Droxia, Hydrea). When taken daily, hydroxyurea reduces the frequency of painful crises and may reduce the need for blood transfusions. Hydroxyurea seems to work by stimulating production of fetal hemoglobin — a type of hemoglobin found in newborns that helps prevent the formation of sickle cells. Hydroxyurea increases your risk of infections, and there is some concern that long-term use of this drug may cause tumors or lekumia in certain people. However, this hasn't yet been seen in studies of the drug.
    Hydroxyurea was initially used just for adults with severe sickle cell anemia. Studies on children have shown that the drug may prevent some of the serious complications associated with sickle cell anemia. But the long-term effects of the drug on children are still unknown. Your doctor can help you determine if this drug may be beneficial for you or your child.

Assessing stroke risk

Using a special ultrasound machine (transcranial), doctors can learn which children have a higher risk of stroke. This test can be used on children as young as 2 years, and those who are found to have a high risk of stroke are then treated with regular blood transfusions.

Vaccinations to prevent infections

Childhood vaccinations are important for preventing disease in all children. But, these vaccinations are even more important for children with sickle cell anemia, because infections can be severe in children with sickle cell anemia. Your doctor will make sure your child receives all of the recommended childhood vaccinations. Vaccinations, such as the pneumococcal vaccine and the annual flu shot, are also important for adults with sickle cell anemia.

Blood transfusions

In a red blood cell transfusion, red blood cells are removed from a supply of donated blood. These donated cells are then given intravenously to a person with sickle cell anemia.
Blood transfusions increase the number of normal red blood cells in circulation, helping to relieve anemia. In children with sickle cell anemia at high risk of stroke, regular blood transfusions can decrease their risk of stroke.
Blood transfusions carry some risk. Blood contains iron. Regular blood transfusions cause an excess amount of iron to build up in your body. Because excess iron can damage your heart, liver and other organs, people who undergo regular transfusions may need treatment to reduce iron levels. Deferasirox (Exjade) is an oral medication that can reduce excess iron levels.

Supplemental oxygen

Breathing supplemental oxygen through a breathing mask adds oxygen to your blood and helps you breathe easier. It may be helpful if you have acute chest syndrome or a sickle cell crisis.

Stem cell transplant

A stem cell transplant, also called a bone marrow transplant, involves replacing bone marrow affected by sickle cell anemia with healthy bone marrow from a donor. Because of the risks associated with a stem cell transplant, the procedure is recommended only for people who have significant symptoms and problems from sickle cell anemia.
If a donor is found, the diseased bone marrow in the person with sickle cell anemia is first depleted with radiation or chemotherapy. Healthy stem cells from the donor are filtered from the blood. The healthy stem cells are injected intravenously into the bloodstream of the person with sickle cell anemia, where they migrate to the bone marrow cavities and begin generating new blood cells. The procedure requires a lengthy hospital stay. After the transplant, you'll receive drugs to help prevent rejection of the donated stem cells.
A stem cell transplant carries risks. There's a chance that your body may reject the transplant, leading to life-threatening complications. In addition, not everyone is a candidate for transplantation or can find a suitable donor.

Treating complications

Doctors treat most complications of sickle cell anemia as they occur. Treatment may include antibiotics, vitamins, blood transfusions, pain-relieving medicines, other medications and possibly surgery, such as to correct vision problems or to remove a damaged spleen.

Experimental treatments

Scientists are studying new treatments for sickle cell anemia, including:
  • Gene therapy. Because sickle cell anemia is caused by a defective gene, researchers are exploring whether inserting a normal gene into the bone marrow of people with sickle cell anemia will result in the production of normal hemoglobin. Scientists are also exploring the possibility of turning off the defective gene while reactivating another gene responsible for the production of fetal hemoglobin — a type of hemoglobin found in newborns that prevents sickle cells from forming. Potential treatments using gene therapy are still a long way off, however. No human trials using genes specifically for sickle cell have yet been done.
  • Nitric oxide. People with sickle cell anemia have low levels of nitric oxide in their blood. Nitric oxide is a gas that helps keep blood vessels open and reduces the stickiness of red blood cells. Treatment with nitric oxide may prevent sickle cells from clumping together. Studies on nitric oxide have had mixed results so far.
  • Drugs to boost fetal hemoglobin production.Researchers are studying various drugs to devise a way to boost the production of fetal hemoglobin. This is a type of hemoglobin that stops sickle cells from forming.
  • Statins. These medications, which are normally used to lower cholesterol, may also help reduce inflammation. In sickle cell anemi, statins may help blood flow better through blood vessels.

LIFESTYLE AND HOME REMEDIES

If you carry the sickle cell trait, you may wish to see a genetic counselor before trying to conceive a child. A genetic counselor can help you understand your risk of having a child with sickle cell anemia. He or she can also explain possible treatments, preventive measures and reproductive options.



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