Acute chest syndrome is a potentially serious lung disease common in children and adults with sickle cell disease. The symptoms can be mild, but they can also constitute a medical emergency. To be diagnosed with acute chest syndrome, the patient must experience fever or new respiratory symptoms and have specific changes on the chest x-ray.
Sickle cell disease affects the hemoglobin in red blood cells, causing them to be crescent or sickle-shaped instead of the normal round and smooth shape. Sickle cells do not move easily throughout the blood vessels and can block blood flow. These blocked vessels cause many serious problems, including infections, stroke, and periods of significant, ongoing pain. Acute chest syndrome occurs when the sickle cells affect the blood vessels in the lungs.
Pulmonary infection is often associated with acute chest syndrome. One study identified multiple infectious organisms in cases of acute chest syndrome, with bacterial infections being the most common overall and viral infections being most common in children under 10.Infections can precipitate an episode of acute chest syndrome by causing inflammation in the lungs, making it even more difficult for sickle cells to pass through.
Another condition that can lead to acute chest syndrome is a pulmonary fat embolism, which can occur with or without an accompanying infection. During pain crises, small droplets of fat are released into the blood. These droplets make their way to the lungs, where they cause inflammation and injury in the air sacs.
A third condition connected to acute chest syndrome and sickle cell disease is pulmonary infarction. One major study showed this event causes 16 percent of acute chest syndrome episodes. Pulmonary infarction occurs because the sickle cells adhere to the small cells lining the blood vessels in the lungs. Blockages result, cutting off the blood supply to parts of the lung tissue.
Episodes of acute chest syndrome vary drastically with age. Acute chest syndrome is most common in children under 10. In this age group, pulmonary infarctions are the most common trigger, and children present with wheezing, cough, and fever.
Adults and older children have chest pain, shortness of breath, and lower oxygen saturation. In adults, acute chest syndrome is more often precipitated by fat embolism. Different areas of the lungs are affected in adults and children, too. In adults, it usually affects the lower lobes of the lungs or multiple areas, while the upper and middle lobes are involved in children.
The statistics on acute chest syndrome show that it is the most common pulmonary disorder in people with sickle cell disease. Half of the people with sickle cell disease have at least one episode of acute chest syndrome, and incidence peaks with children between two and four. It is the most common cause of death from sickle cell disease.
Rapid diagnosis of acute chest syndrome is crucial. It often starts within 24 to 72 hours of the beginning of a pain crisis; hospitalized patients must be monitored closely for low oxygen saturations, rapid breathing, elevated heart rate, and fever.
Doctors will order a chest x-ray for patients with suspected acute chest syndrome who have fever or chest pain. X-ray changes are not always present at the onset of the syndrome, so doctors will likely begin treatment even if the chest x-ray is normal. Blood tests can determine the severity of the episode by showing how much hemoglobin and platelets have decreased.
Other possible diagnostic tests for acute chest syndrome include chest CT scans, breathing and circulation scans, and imaging to check for pulmonary emboli. Hospitalized patients with acute chest syndrome need a blood type screen, as the need for an emergency transfusion is high. Doctors should rule out other life-threatening conditions, including pulmonary embolus and pneumonia.
Early treatment of acute chest syndrome correlates to a shorter hospital stay, better outcomes, and less chance of recurrence. Interventions include pain management, IV fluids, supplemental oxygen, blood transfusions, and antibiotics. Patients should do breathing exercises every two hours to prevent atelectasis — the collapsing of the small air sacs in the lungs. In cases where the patient also has asthma, bronchodilators can help.
Acute chest syndrome is the second most common cause of hospitalization in patients with sickle cell disease. As many as 20 percent of patients hospitalized with a pain crisis develop acute chest syndrome within three days.
Most cases resolve on their own with supportive care, but some progress rapidly, causing acute respiratory failure. The most common causes of death for patients with acute chest syndrome are pulmonary emboli and pneumonia. One study showed as many as 11 percent develop neurological complications.
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