Acute chest syndrome (ACS) is one of the most severe complications of sickle cell disease (SCD), being the second most cause of hospitalization as well as the commonest cause of death.
In a clinical sense, acute chest syndrome resembles pneumonia is every way. The only distinguishing feature is that the former occurs exclusively among people living with sickle cell disease.
Acute chest syndrome can occur suddenly or as an insidious complication of a vaso-occlusive crisis or commonly following abdominal surgery. Risk factors include previous episodes of acute chest syndrome and asthma.
The National Acute Chest Syndrome Study Group performed a landmark study to delineate the clinical, laboratory and radiographic features of acute chest syndrome.
That said, ACS typically presents with sudden onset of cough, shortness of breath, fast breathing, chest indrawing, rales as well as other signs and symptoms of lower respiratory tract disease with a new pulmonary infiltrate on a chest radiograph.
Children often present with a fever and evidence of middle or upper lung lobe involvement. On the other hand, adults present with multiple lobes involved, with no fevers.
Commonly, acute chest syndrome is due to an infection, either bacterial, viral, Mycoplasma or Chlamydia.
In the few cases, where there is no evidence of infections, it might be due to;
-a complication of bone marrow fat embolism,
– pulmonary oedema,
-aggregation of sickled cells in the intrapulmonary vasculature, or
-a lung collapse (atelectasis).
It is not uncommon for these patients presenting with haemoglobin levels below the baseline.
In many instances, patients with acute chest syndrome recover within a few days after hospitalization. A few others, however, develop a multiorgan system failure where the kidneys, brain, and liver get involved; death can be an inevitable outcome if care isn’t prompt.
Treatment of ACS entails the use of broad-spectrum antibiotics, oxygen supplementation, bronchodilators, and blood transfusions. Whether corticosteroids and other anti-inflammatory agents have a role to play in the management of acute chest syndrome is still uncertain.
The involvement of more than one lung lobe laboured breathing, and the inability to maintain oxygen saturation above 95% despite supplemental oxygen as well as pleural effusions, should signal a severe course of the disease.
Any person who develops recurrent episodes of acute chest syndrome has an increased risk of developing chronic lung disease.
We note that carrying out incentive spirometry every 2-4 hours for a patient admitted for a vaso-occlusive crisis can prevent acute chest syndrome.
With the above preamble about this complication, let’s get to the recommendations regarding its management. Again, we adopted them from the NHLBI.
- Evaluate people with SCD who develop the acute onset of lower respiratory tract disease signs or symptoms (cough, shortness of breath, tachypnea, retractions, or wheezing) with or without fever for ACS. It should include a chest x-ray and measurement of oxygen saturation by pulse oximetry.
- Hospitalize people with ACS.
- Treat people with SCD who have ACS with an IV cephalosporin, an oral macrolide, and supplemental oxygen. Maintain an oxygen saturation of greater than 95%. Closely monitor for bronchospasm, acute anaemia, and hypoxemia.
- In people with SCA, give simple blood transfusion (10 mL/kg red blood cells) to improve the oxygen-carrying capacity to people with symptomatic ACS whose haemoglobin concentration is >1.0 g/dL below the baseline. If baseline haemoglobin is 9 g/dL or higher, simple blood transfusion may not be required.
- In people with HbSC disease or HbS β+-thalassemia with ACS, make transfusion decisions should in consultation with an SCD expert.
- In all persons with SCD, perform urgent exchange transfusion when there is a rapid progression of ACS as manifested by oxygen saturation below 90 per cent despite supplemental oxygen, increasing respiratory distress, progressive pulmonary infiltrates, or decline in haemoglobin concentration despite simple transfusion. Consult the experts from haematology, critical care, or apheresis specialists—
- Encourage the use of incentive spirometry while awake.