Too Cute To Be Bored: Acute Chest Syndrome

ACS is defined by a new infiltrate on chest X-ray PLUS at least one new sign/symptom: fever, cough, wheezing, tachypnea, hypoxia, or chest pain. It is caused by infection, fat emboli / thrombo-emboli, rib infarction, or lung sequestration of sickled RBCs. Possible iatrogenic causes include aggressive hydration causing pulmonary edema or opioids causing respiratory depression / poor inspiratory effort, and atelectasis.

In those with infectious etiologies, ACS is most commonly caused by atypicals – Chlamydia pneumoniae and Mycoplasma pneumoniae – but certainly can be caused by viral pneumonias or other common bacterial pathogens.

Although you must see a new infiltrate on chest X-ray for the diagnosis, the chest X-ray can lag behind the clinical symptoms, so keep a high index of suspicion.

Think again! Bony ischemia and necrosis may lead to necrotic pieces of bone marrow breaking off and embolizing.

Each of these triggers causes lung injury, V/Q mismatch, and hypoxemia, which themselves promote more inflammatory mediators, erythrocyte adhesion, and vaso-occlusion …  leading to more lung injury, infection, and hypoxemia! It’s a vicious cycle! Vicious!!

This is Miss Maggie Moo. She is a vicious beast. And super-cute.

Despite the multiple etiologies of ACS, it is impossible to know the underlying cause in the ED. So, treat them all: fluids, antibiotics, oxygen, pain control, and possible blood transfusion or exchange transfusion.

• Hypotonic fluids: Oral hydration is best. For IV hydration, hypotonic solutions such as 1/2 NS promote osmotic swelling of cells (one of the only times we really want this effect) to help plump up those sickly sickled cells. Rate: 1.5x maintenance.
• Empiric antibiotics: Cover community-acquired pneumonia (azithromycin, ceftriaxone) and go broad if they have been hospitalized recently.
• Analgesia: Opioids are a mainstay of treatment for our sickle cell patients and should be used here, but be cautious about respiratory depression and poor inspiratory efforts which can worsen the syndrome.

If you hear wheezing, consider albuterol to help calm the inflammatory cascade that is contributing the cycle of viciousness.

Exchange transfusion? Solid evidence is lacking, but in a severe crisis when the hgb level is not too low ( > 9), exchange transfusion can filter out the culprit cells while replenishing with functioning RBCs.

Acute chest syndrome is the leading cause of death in sickle cell patients! Because this is a VICIOUS cycle, they can decomensate quickly and need intubation, transfusions, and a high level of care. Get them to the MICU or a monitored bed.

This is Toby. He enjoys scratching things that shouldn’t be scratched, food, and sleeping.