Dr. Hellman reminds us that “Acute Chest Syndrome is the most common cause of death in sickle cell disease with a case fatality rate of 10%.”
The key to diagnosis acute chest syndrome [which requires prompt specific life saving treatment] is to recognize that hypoxia or any change in respiratory status in a sickle cell disease patient is acute chest syndrome until proven otherwise. Listen to the podcast Best Case Ever 38 Sickle Cell Acute Chest Syndrome by Drs. Ward and Hellman.
The following is from the show notes of Episode 68 Emergency Management of Sickle Cell Disease from Emergency Medicine Cases:
Acute Chest Syndrome
A 35 year old otherwise healthy woman with a known history of sickle cell disease comes in a week after her last uneventful pain crisis with a 2 day history of non-productive cough and gradual onset non-pleuritic severe central chest pain radiating to both shoulders. She admits to being short of breath on exertion. Her vitals show that she is bit tachycardic and dyspneic with a normal blood pressure, an oxygen saturation of 92% on room air and a borderline Temp of 37.8. Her cardiovascular exam is essentially normal and her chest is clear. The chest x-ray, however, shows multilobar infiltrates.
Acute Chest Syndrome is the most common cause of death in sickle cell disease with a case fatality rate of 10%.
Like all classic triads in medicine the classic triad of Acute Chest Syndrome (fever, hypoxia and pulmonary infiltrate) is often not present. However, the presence of any of this triad should raise the suspicion for the diagnosis. Acute Chest Syndrome can present fairly benignly with bronchitis-like or pneumonia-like clinical picture with cough and SOB, but often do not develop a fever. The pain of Acute Chest Syndrome is characterized by a T-shirt distribution.
Any sickle cell patient with hypoxia should be presumed to have Acute Chest Syndrome until proven otherwise.
What makes acute chest syndrome special isn’t so much what is happening, it’s where it’s happening – sickling blocks blood flow causing local hypoxemia and ischemia and in Acute Chest Syndrome the sickling is in the pulmonary vasculature. As a result the patient becomes more hypoxic, which drives more sickling, which drives more vaso-occlusion, which drives more hypoxia, so that a visious cycle is created leading to a spiral ending in death.
Differentiating sickle cell pain crisis with chest pain and acute chest syndrome
A sickle cell patient with isolated chest pain without any other symptoms can be safely presumed to be suffering from a sickle pain crisis, whereas any associated respiratory symptoms should raise the possibility of an Acute chest Syndrome.
Any degree of hypoxia, even if the chest x-ray is initially normal, should be considered an Acute Chest Syndrome until proven otherwise.
Have a low threshold for admission for any sickle cell patient with a new infiltrate on chest x-ray or any degree of hypoxia.
Why is it important to diagnose Acute Chest Syndrome Early?
The sooner the patient with an Acute Chest Syndrome is diagnosed the sooner they can receive life-saving treatment with a simple red cell transfusion or exchange transfusion in consultation with a hematologist. In addition to usual resuscitative measures, patients should be initiated on broad spectrum empiric antibiotics.
Indications for Exchange Transfusion in Acute Chest Syndrome:
Severe Acute Chest Crisis
Rapid or significant clinical deterioration
Worsening chest radiography
PO2 < 70mmHg
Baseline hemoglobin >90 (which precludes use of simple transfusion due to risk of hyperviscosity)
Evidence-Based Management of Sickle Cell Disease: Expert Panel, 2014 [Full Text PDF]