In a patient with sickle cell disease who develops shortness of breath, chest pain, and a decrease in oxygen saturation, what is the most likely cause?

Acute Chest Syndrome (ACS) is the Most Likely Cause

In a patient with sickle cell disease presenting with shortness of breath, chest pain, and oxygen desaturation, acute chest syndrome is the most likely and most critical diagnosis to consider—this is a leading cause of death in SCD and requires immediate emergency evaluation and treatment 1, 2.

Why ACS is the Primary Concern

ACS is defined by respiratory symptoms and/or fever with a new radiodensity on chest imaging in a patient with SCD 3. The clinical presentation described—SOB, chest pain, and SpO2 drop—matches the classic triad, though notably:

• Severe disease indicators include significant decline in hemoglobin and/or oxygen saturations (SpO2 ≤94% or several percentage points below baseline) 3
• The spectrum ranges from mild respiratory illness to acute respiratory distress syndrome 4
• Adults typically present differently than children: adults are often afebrile, complain of shortness of breath, chills, and severe pain, whereas young children present with fever and cough 5
• Severe hypoxia occurs in 18% of adults and cannot be predicted by examination or laboratory findings alone 5

Critical Clinical Pitfalls

Do not wait for chest X-ray confirmation to begin treatment—the infiltrate may not be visible on initial presentation 6. The patient can deteriorate rapidly with progression to pulmonary failure and death 6.

Approximately 50% of adults have a pain event in the 2 weeks preceding ACS 5, so this may develop during hospitalization for vaso-occlusive crisis rather than as the presenting complaint.

Other Important Differential Considerations

While ACS is the priority, also evaluate for:

• Pulmonary embolism: Patients with SCD have increased risk of venous thromboembolism, particularly with elevated tricuspid regurgitation velocity 7
• Acute myocardial infarction: Older adolescents and adults with SCD can develop AMI at relatively early age, usually without traditional risk factors 1, 2
• Pulmonary hypertension: Can present with similar symptoms and carries high mortality risk 7

Immediate Management Algorithm

Emergency transfer to acute care setting is mandatory 1, 2:

1. Oxygen supplementation to maintain SpO2 above baseline or ≥96% 8
2. Aggressive analgesia with parenteral opioids (morphine) via scheduled dosing or patient-controlled analgesia 6
3. Incentive spirometry every 2 hours to prevent hypoventilation 8, 6
4. Empiric antibiotics covering atypical pathogens 9
5. Adequate hydration (avoid both dehydration and fluid overload) 3
6. Bronchodilators if history of asthma or acute bronchospasm 3

Transfusion Decision-Making

For severe ACS (rapidly falling hemoglobin, severe hypoxia, or requirement for invasive respiratory support):

• Automated or manual red cell exchange (RCE) is preferred over simple transfusion 3
• Automated RCE more rapidly reduces HbS levels 3
• Target HbS ≤30% to prevent right heart failure and mortality 10

For moderate ACS:

• Simple transfusion, automated RCE, or manual RCE are all acceptable 3
• Consider RCE for rapidly progressive disease or high pretransfusion hemoglobin that precludes simple transfusion 3

Monitoring for Deterioration

• Continuous oxygen saturation monitoring until maintained at baseline in room air 8
• Regular temperature checks (spike may indicate ongoing sickling) 8
• Serial hemoglobin measurements (watch for acute decline) 3
• Consider point-of-care ultrasound to assess for acute pulmonary hypertension (TR jet velocity >4 m/s indicates high mortality risk) 10

The mortality rate in adults with ACS is four times higher than in children 5, and fatal cases generally develop rapid pulmonary failure 5. Early recognition and aggressive treatment are crucial to prevent death 3.