Sickle Cell and Acute Chest Syndrome Clinical Pathway — Inpatient
Etiology of ACS
ACS is a common form of acute lung injury in patients with SCD.
Three major causes of ACS are infection, embolization of bone marrow fat and intravascular sequestration of hemolyzed RBCs.
It is believed that infection, the most common cause, may incite an excessive inflammatory response in patients with SCD causing acute lung injury. Fat emboli are commonly associated with severe VOC involving multiple bones, especially long bones. Bone marrow infarction and edema of causes bone marrow necrosis and its contents, including fat are released into the bloodstream, hence setting up the stage for pulmonary emboli. Pulmonary embolization leads to severe inflammation in the lung causing V-Q mismatch and hypoxemia. The resultant hypoxemia causes further deoxygenation of hemoglobin S increasing RBC sickling causing a vicious cycle of a lung infarction, inflammation, and atelectasis exacerbating existing ventilation-perfusion mismatch and hypoxemia. Pain crises often precede the development of ACS.