Sickle Cell Anemia

Sickle Cell Anemia

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Sickle Cell Anemia

Introduction and Prevalence

Sickle cell anemia is a severe form of hemolytic anemia, which is potentially life threatening and begins to manifest in early childhood. Sickle cell anemia is a form of qualitative hemoglobinopathy, meaning it is one of the diseases caused by mutations of genes encoding the globin chains of the molecule, hemoglobin. The defect is a mutation in the gene that codes for globin chains in the molecule hemoglobin. Hemoglobin is critical in normal delivery of oxygen to tissues. Sickle cell anemia results from the substitution of glutamic acid to valine at position 6 of the beta globin chain. The pattern of inheritance is autosomal recessive, for a child to get the disease; they have to receive a sickle gene from each parent. The homozygous form results in the production of abnormal beta hemoglobin chains that make hemoglobin S (HbS coded as SS), resulting in the clinical syndrome of sickle cell disease. The heterozygous form on the other hand, results in the production of a mixture of normal and abnormal beta chains making normal HbA and HbS, resulting in sickle cell trait which is clinically asymptomatic.

Sickle cell anemia has a higher prevalence rate in Sub-Saharan Africa as compared to the rest of the world. South America, the Caribbean, Central America, Saudi Arabia, India and Mediterranean countries including Turkey, Italy and Greece follow closely. Data from the Centers for Disease Control estimate that sickle cell disease affects approximately 100,000 Americans. It indicates that sickle cell disease occurs in one out of every 365 African-American births and one out of every 16300 Hispanic American births. The prevalence of sickle cell anemia in the United States of America is higher among African Americans, with a frequency of sickle cell trait in this population being at 8%. The occurrence of the homozygous form of sickle cell anemia among this population is 1 in 400. The prevalence of this disease is higher in Tropical Africa with a heterozygote frequency of over 20%.

Pathophysiology of the Disease

The substitution of glutamic acid to valine at position 6 of the beta globin chain results in the formation of HbS, which is susceptible to polymerization when deoxygenated. There is polymerization of hemoglobin molecules to form pseudo crystalline structures called ‘tactoids’ which are a gelatinous network of fibrous polymers that distort the cell membrane, increase viscosity and cause dehydration due to leakage of potassium and influx of calcium. They lead to production of sickle shaped red blood cells, which have altered sticky membranes that adhere abnormally to the endothelium of small venules and lose pliability to pass through small capillaries. Polymerization is reversible upon re-oxygenation, but the distortion of cell membrane may be permanent and the red blood cells assume a sickled shape.

The abnormalities in red blood cells precipitate unpredictable episodes of microvascular occlusion and premature destruction of red blood cells as in hemolytic anemia. The spleen destroys abnormally shaped red blood cells leading to hemolysis and results in hemolytic anemia. The rigid cells that are adherent clog small capillaries leading to ischemia of tissues, acute pain and gradual end organ damage. The veno-occlusive component dominates the clinical course of the disease. The concentration of sickle-cell hemoglobin determines the rate of formation of tactoids. The presence of other types of hemoglobin may accelerate or limit this process. The abnormal hemoglobin C variant accelerates polymerization more readily as compared to the variant hemoglobin A. Persistent fetal hemoglobin in the form of hemoglobin F strongly inhibits polymerization; hence, its presence in a sickle cell patient offers a better prognosis. Other conditions that precipitate sickling apart from hypoxia include acidosis, dehydration and infection.

Signs and Symptoms

The clinical presentation of sickle cell disease is due to the underlying pathophysiologic mechanisms. The clinical features maybe in the form of various features associated with the syndrome. Acute pain, also known as painful crisis is a major symptom that occurs during vaso-occlusive crisis in the bone, especially where there is active marrow including hands and feet (dactylitis) in children, or the humeri, femora, ribs, pelvis and vertebrae in adults. Symptoms that accompany pain include tachycardia, fever and sweating. Pain may also occur in other parts of the body and may last from a few hours up to two weeks. Dyspnea due to respiratory failure caused by acute chest syndrome is another symptom of sickle cell disease. This may follow acute pain experienced in vaso-occlusive crisis that leads to infarction of bone marrow and fat embolism to the lungs leading to respiratory failure. Other symptoms in acute chest syndrome include chest pain, fever tachycardia and cough.

On clinical examination, the examiner may elicit various signs that point towards sickle cell disease. Tenderness on affected bone and on the chest and other parts of the body where the patient complains of pain. Anemia due to haemolysis of red blood cells may reveal pallor in mucous membranes such as the conjunctiva and on the tongue. Granulocytosis is another notable hematological sign. Auto-splenectomy due to recurrent splenic infarction caused by the susceptibility of the splenic vascular beds to sickling. On examination, there will be absence of the spleen in its usual anatomical location.

Hemorrhage of retinal vessels, neovascularization and eventual detachment may occur due to repeated occlusion of retinal vessels and may be notable during fundoscopy. Isosthenuria is another sign that may result from renal papillary necrosis due to vessel obstruction. Widespread renal tubular necrosis may precipitate renal failure and its complications. Aseptic avascular necrosis of the humeral and femoral heads, chronic arthropathy and chronic osteomyelitis may result from ischemia of bones and joints. Cerebrovascular accident, mainly the hemorrhagic form, is a common sign in children. Priapism is a sign that may occur in males due to infarction of the venous outflow tracts of the penis. Chronic lower leg ulcers are another common sign most likely due to ischemia and superinfection in peripheral circulation.

Sickle cell trait is normally asymptomatic. Symptoms that may occur include painless hematuria in adolescent males probably because of papillary necrosis. Isosthenuria may occur with this sign. There have been reports of death due to exposure to high altitudes, extremes of temperature, exercise and physical stress. There should be avoidance of these stress factors by individuals with sickle cell trait.

Treatment Available

Prophylaxis is an integral part of management of patients with sickle cell disease. This incorporates daily folic acid and penicillin V for protection against pneumococcal infection in case of auto-splenectomy. Vaccination against pneumococcus, meningococcus, Hemophilus influenza B, hepatitis B and Seasonal influenza is important. In malaria endemic areas, prophylaxis against malaria infection is through administration of Proguanil along with the above prophylactic measures.

Management of vaso-occlusive crisis is through aggressive rehydration, oxygen therapy based on the requirement, adequate analgesia using opioids and administration of prophylactic antibiotics in case infection is present. Administration of definitive antibiotics is possible after blood cultures. Transfusion with blood and blood products as a simple top up transfusion during aplastic or sequestration crises, and the development of a regular transfusion program is essential to suppress production of HbS. Exchange transfusion is important in life threatening cases. There is room for agents that increase the levels of HbF in the blood, which inhibits the level and rates of polymerization of HbS hence reducing sickling. Such agents include hydroxyurea, which is the mainstay of therapy for patients with severe symptoms. Bone marrow transplantation is a possible measure to relieve the sickle cell patient of pain, and to boost their hemopioesis.

Life Expectancy Associated with the Disease

In Africa, most children do not survive to adulthood without medical attention. With standard medical care, about 15% die by age 20 years and 50% by the age of 40 years. Research by , the median age at death for homozygous females was 42 years and for males was 48 years. Individuals with sickle cell trait have a higher life expectancy since they are asymptomatic. According to , people with sickle cell disease have a 20-30 years old lower life expectancy as compared to people without sickle cell disease. Deaths related to sickle cell among African-Americans younger than four years old fell by 42% between 1999 and 2002.

Nursing Care for a Patient with the Disease.

There are several important aspects for consideration during provision of nursing care for the patient. There is need for continuity of care for the patient after discharge from the hospital into the hands of family or any other caregiver at home. The first nursing intervention is to obtain history of past and present pain management, to find out alleviating factors and to determine if the patient had this kind of pain before. There is need to conduct pain assessment every 15 to 30 minutes and based on the medication dosing interval as soon as pain is well controlled. This assessment is subjective based on what the child reports, based on pain scales, physiological indicators that are the vital signs and behavioral indicators.

Another nursing intervention is the administration of pharmacological interventions including anti-inflammatory analgesics and narcotics, taking note of the side effects of each aand the patient’s allergies prior to administration. Tolerance, addiction and dependence are key issues for consideration during and after administration. Administration of non-pharmacological interventions to relieve pain including heat through a heating pad, shower or bath, massage, distraction and guided imagery is essential.

In addition to these, another nursing intervention is to encourage hydration in various ways. This is through both intravenous and oral one to one and a half times hourly maintenance fluid requirements. There should be care to avoid fluid overload that may precipitate acute chest syndrome. Nursing care should aim at preventing complications associated with sickle cell disease through incentive spirometry while considering age appropriate alternatives, noting signs such as cough and deep breathing, and assessment of patient mobility. Nursing care incorporates provision of patient and family education on how to prevent further episodes through adequate hydration, avoidance of extreme temperatures, acidosis and hypoxia. In addition to these, how to manage them when they occur in mild form, medication administration, side effects, non-pharmacologic pain management, when to seek healthcare services.

References

Centers for Disease Control and Prevention. (n.d.). Sickle Cell Disease (CDC). Atlanta.

Jakubik, L. D. (2010). Nursing Care of the Child with Sickle Cell Disease: Acute Complications. Nursing of Children Network Conference 2010.

Longo, D. L., Kasper, D. L., Jameson, J. L., Fauci, A. S., Hauser, S. L., & Loscalzo, J. (2012). Harrison’s Principles of Internal Medicine. McGraw-Hill.

Platt, O. S., Brambilla, D. J., Rosse, W. F., Milner, P. F., Castro, O., Steinberg, M. H., & Klug, P. P. (1994). Mortality in Sickle Cell Disease-Life Expectancy and Risk Factors for Early Death. New England Journal of Medicine.

Walker, B. R., Colledge, N. R., Ralston, H. S., & Penman, I. (2014). Davidson’s Principles and Practice of Medicine. Churchill Livingstone.