Sickle Cell Anemia 1

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Sickle cell disease is an inherited autosomal recessive genetic condition. A specific mutation in the hemoglobin gene alleles on chromosome 11 leads to the formation of HbS instead of HbA.

Back 1

In sickle cell disease, the patient has two HbS gene alleles, one inherited from each parent, usually resulting in 80% to 100% of the hemoglobin being HbS. When both parents are carriers of the sickle cell trait, there is a 25% chance with each pregnancy of producing an off spring with SCA.

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In the United States it is estimated that 1 in 12 African-Americans carry the trait. Universal screening of newborns for SCD has become standard in all 50 states and territories using the Sickledex test and Hemoglobin Electrophoresis test.

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It provides early identification of these children before complications develop. Early diagnosis facilitates parental education regarding the importance of immunizations, penicillin prophylaxis, detection of splenomegaly, and the need to report fever and increasing pallor, all of which may be lifesaving.

Front 3

The basic defect responsible for the sickling of erythrocytes is contained in the globin fraction of hemoglobin. Under conditions that cause an increased demand for oxygen in the body (dehydration, vomiting, diarrhea, trauma,hypoxia, fever, exposures to extreme hot and cold and emotional/physical stress) , the amino acid of the β chain changes.

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This then distorts the cell membrane so that the cell changes from a pliable disk to a crescent- or sickle-shaped RBC.

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The sickled forms of the RBC are associated with much greater viscosity than those with the normal rounded structure. In most instances the sickling response is reversible with adequate oxygenation and hydration.

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RBCs with HgbS can sickle and unsickle under appropriate conditions. After repeated cycles of sickling and unsickling, the RBCs become irreversibly sickled

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A patient experiencing a Vaso-occlusivecrisis will

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have localized or generalized pain to muscles, arthralgia, acute abdominal pain from visceral hypoxia,

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A patient experiencing a Vaso-occlusive crisis will have

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a priapism which is an unwanted painful penile erection. The cause of priaprism is excessive vascular engorgement in erectile tissue. The condition is very painful and can last for hours. During the priapism episode, the patient usually cannot urinate.

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Children under the age of 2 years often develop dactylitis, also known as hand-foot syndrome.

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It is caused by infarction of short tubular bones and is characterized by pain and swelling of the soft tissue over the hands and feet. . It usually resolves spontaneously within a couple of days to weeks. During this crisis , the pain is often

migratory, with the presence of a low-grade

fever.

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Due to the sickling, thepatient will develop jaundice and possible hematuria.

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Jaundice results from RBC destruction and release of bilirubin.

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To assess for jaundice in patients with darker skin,

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inspect the roof of the mouth for a yellow appearance and examine the sclera closest to the cornea.

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Due to the obstruction, the patient can develop the life threatening signs associated with stroke and chest pain, known as

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chest syndrome, that is associated with a MI.

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Medical management of a crisis is directed at supportive, symptomatic, and specific treatments.

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bed rest to minimize energy expenditure & to

improve oxygen utilization,--hydration,

electrolyte replacement (since hypoxia results in metabolic acidosis, which also promotes sickling),--analgesia for pain from vasoocclusion, blood transfusion to treat anemia & to reduce the viscosity of the sickled blood, & antibiotics

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Oxygen administration is usually not effective in reversing sickling or reducing pain because

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the oxygen is notable to reach the enmeshed sickled RBCs through the clogged vessels. Inaddition, prolonged administration of oxygen can depress bone marrow activity,which further aggravates the anemia.

Front 13

Once a SCD patient begins to experience a Vasoocclusivecrisis episode,

they are told to rest, begin drinking water and take the prescribed pain medication.

If crisis continues, repeat process a second time before coming to hospital.

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However, if patient is

feverish, pale or experiencing cerebral vascular accident symptoms or chest syndrome pain; then they are to seek immediate medical help.

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Hydroxyurea (HU) is the only effective drug to treat adult SCD patients

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to reduce the incidence of recurrent severe

painful episodes and acute chest syndrome by increasing the concentration of HgbF and ultimately to reduce complications.

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Hydroxyurea is teratogenic (can cause birth defects).

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Teach sexually active women of childbearing age using this drug to adhere to strict contraceptive measures while taking hydroxyurea and for 1month after the drug is discontinued.

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Vassoocclusive crises and sickle cell anemia lead to multiple complications

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Complications to the head might include

a cerebrovascular accident, which is a sudden and severe complication, often withno related illnesses. Sickled cells block the major blood vessels in the brain,which results in cerebral infarction causing variable degrees of neurologic

impairment.

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Vassoocclusive crises and sickle cell anemia lead to complications

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Repeat strokes causing progressively greater brain damage in children who have already experienced one stroke. neurologic symptoms can indicate a minor cerebral insult, such as headache, seizures, or visual disturbances. Blindness is usually the result of progressive retinopathy and retinal detachment.

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Vassoocclusive crises and sickle cell anemia lead to complications

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Complications in the lung include frequent

pneumonia with atelectasis.

Another seriouscomplication is acute chest syndrome which is clinically similar to pneumonia.

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Vassoocclusive crises and sickle cell anemia lead to complications. A cute chest syndrome is defined as

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a new pulmonary infiltrate on chest x-ray of a SCD patient that may be accompanied by chest pain, fever, cough, tachypnea,wheezing, and hypoxia.

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Researchers believe that a VOC or infection

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results in sickling in the small blood vessels of the lungs, with ensuing occlusion,stasis, and anemia.

Repeated episodes of chest syndrome may cause restrictivelung disease and pulmonary hypertension.

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Heart problems are mainly attributable to the stress of chronic anemia, which can eventually result indecompensation and heart failure.

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Cardiomegaly is visualized on a chest X-rayand a systolic flow murmur is frequently present as a consequence of the anemia.A serious cardiac issue resulting from occlusion is the potential for a myocardial infarction.

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Bone changes include hyperplasia and

congestion of the bone marrow, which result in osteoporosis. As a result ofthe weakening of bone, skeletal deformities, particularly lordosis and kyphosis, may occur. Because of chronic

hypoxia, the bone becomes susceptible to

osteomyelitis.

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Avascular necrosis of the femoral head from chronic ischemia is an occasional problem.

Front 23

Kidney abnormalities are probably the result of the same cycle of congestion of glomerular

capillaries and tubular arterioles with sickled cells, tissue necrosis, and eventual scarring.

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The principal results of kidney ischemia are

hematuria, frequent urinary tract infections,

pyelonephritis, and nephrotic syndrome. Kidney failure can result.

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The liver is also altered in form and function.

Liver failure and necrosis are the result of

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severe impairment of hepatic blood flow from anemia and capillary obstruction. The rapid

destruction of RBCs often results in the

development ofobstructive jaundice and gallstones.

Front 25

If recurrent episodes of right upperabdominal pain occur,

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cholecystectomy may be indicated. Initially the spleen may become enlarged (called splenomegaly) from congestion and engorgement with sickled cells. Life-threatening

Front 26

Splenic sequestration crisis:

After numerous crisis events, the functioning cells are gradually replaced by fibrotic tissue

until, by the age of 5 years, the spleen has decreased in size and has been totally replaced by a fibrous mass.

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Without the spleen to filter bacteria and to promote the release of large numbers of phagocytic cells, these individuals are highly susceptible to infection.

Front 27

Many adults with SCD have skin ulcers on the lower legs that are caused by poor perfusion, especially on the outer sides and inner aspect of the ankle or the shin.

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These lesions often become necrotic or infected, requiring débridement and antibiotic therapy. Inspect the legs and feet for ulcers or darkened areas that may indicate necrotic tissue.