Acute Chest Syndrome in Sickle Cell Disease

What happens in acute chest syndrome

In sickle cell disease, red blood cells contain abnormal hemoglobin that makes them stiff and sickle-shaped when oxygen is low. In the lungs, sickled cells block small blood vessels. Areas of lung then receive less blood and oxygen, which causes more sickling, a vicious cycle. Infection, fat released from bone marrow during a pain crisis, and shallow breathing from rib pain or opioids all add to the damage.

Episodes often start 2 to 3 days into a hospital stay for a pain crisis, so doctors watch closely for it.

Symptoms

• chest pain, often sharp and worse with breathing
• fever
• cough
• shortness of breath or fast breathing
• wheezing
• low oxygen levels
• pain in the back, ribs or belly
• in young children, fever and cough may be the only signs

Symptoms can worsen within hours, and up to about 1 in 5 adults with acute chest syndrome need intensive care.

Causes and risk factors

• Infections: bacteria such as Chlamydophila pneumoniae, Mycoplasma pneumoniae and Streptococcus pneumoniae, and viruses including RSV, influenza and COVID-19
• Fat embolism: fat from infarcted bone marrow travels to the lungs during a severe pain crisis
• Shallow breathing from chest wall pain, opioids or abdominal surgery
• Pulmonary blood vessel blockage by sickled cells
• Asthma, which increases risk
• Higher baseline hemoglobin and white cell counts and the HbSS genotype
• Recent surgery, especially abdominal

Diagnosis

• Chest X-ray: a new infiltrate in at least one lung segment confirms the diagnosis together with symptoms. Changes may lag behind symptoms, so X-rays are repeated.
• Oxygen saturation and blood gases
• Blood count: hemoglobin often drops, white cells and platelets change
• Blood and sputum cultures, viral swabs
• CT pulmonary angiogram if a pulmonary embolism is suspected

Treatment

1. Oxygen to keep saturation at or above about 95%, or the target set by the hematology team.
2. Antibiotics covering typical and atypical pneumonia organisms, usually a cephalosporin plus a macrolide.
3. Pain control with opioids and other medicines, balanced to avoid suppressing breathing.
4. Incentive spirometry: deep breathing using a device every 2 hours while awake, to open up the lungs.
5. Blood transfusion: a simple transfusion improves oxygen delivery. An exchange transfusion, which removes sickled cells and replaces them with donor cells, is used for severe or worsening cases.
6. IV fluids with care, as too much fluid can worsen lung congestion.
7. Bronchodilators for wheeze or asthma.
8. Intensive care and breathing support when oxygen falls despite treatment.

Complications

Acute chest syndrome can lead to respiratory failure, stroke, multi-organ failure and death. Repeated episodes contribute to chronic lung disease and pulmonary hypertension.

Prevention

• Hydroxyurea reduces the frequency of acute chest syndrome and pain crises and is recommended for most people with HbSS from infancy.
• Chronic transfusion programs for people with repeated severe episodes.
• Incentive spirometry during every pain crisis and after surgery.
• Vaccines: pneumococcal, influenza, COVID-19 and other routine vaccines, plus penicillin prophylaxis for young children.
• Preoperative transfusion before major surgery.
• Good asthma control.
• Newer medicines and gene therapies for sickle cell disease may reduce complications for some patients.

Outlook

Most people recover with prompt treatment, usually within a week. Early recognition and treatment are the most important factors in outcome. People who have had one episode are more likely to have another, so prevention matters. See sickle cell disease and sickle cell crisis for long-term management.

Frequently asked questions

What is acute chest syndrome?

Acute chest syndrome is a serious lung complication of sickle cell disease. It is defined as a new shadow on a chest X-ray with chest pain, fever, cough, wheezing, fast breathing or low oxygen. It can worsen quickly and needs hospital treatment.

What triggers acute chest syndrome?

Common triggers are lung infections, fat from bone marrow released during a pain crisis, blood vessel blockage by sickled cells, and shallow breathing caused by rib pain, opioids or surgery. Asthma and the HbSS form of sickle cell disease raise the risk.

How is acute chest syndrome treated?

Treatment includes oxygen, antibiotics, pain control, deep breathing with an incentive spirometer, IV fluids given carefully, and blood transfusion. Severe cases need exchange transfusion and intensive care. Most people improve within several days with early treatment.

Can acute chest syndrome be prevented?

The risk can be reduced. Hydroxyurea lowers how often it happens. Using an incentive spirometer during pain crises and after surgery, keeping vaccines up to date, controlling asthma and having a transfusion before major surgery all help.

Is acute chest syndrome the same as pneumonia?

Not exactly. Infection causes many cases and the X-ray can look like pneumonia, but acute chest syndrome also involves blocked blood vessels and fat emboli in the lungs. Because of this, it needs specific treatments such as transfusion in addition to antibiotics.