Can aspiration cause pulmonary effusion?

Aspiration as a Cause of Pleural Effusion

Yes, aspiration can cause pleural effusion, particularly when it leads to pneumonia or chemical pneumonitis with subsequent inflammatory response that affects the pleural space. 1

Pathophysiology of Aspiration-Related Pleural Effusions

Aspiration can lead to pleural effusion through several mechanisms:

• Aspiration pneumonia occurs when bacteria from the oropharynx or stomach enter the lungs, causing infection that can spread to the pleural space 1, 2
• Chemical pneumonitis results from aspiration of sterile gastric contents, causing direct inflammatory damage to lung tissue that can extend to the pleural space 2, 3
• The inflammatory response to either bacterial or chemical aspiration can increase pleural membrane permeability, leading to exudative pleural effusion 2

Clinical Presentation and Diagnosis

When aspiration leads to pleural effusion, the following characteristics are typically observed:

• Parapneumonic effusions associated with aspiration pneumonia are usually unilateral 1
• In cases of aspiration pneumonia with pleural involvement, the pleural fluid may show:
  • Low pH (<7.2) 1
  • High LDH (>1000 IU/l) 1
  • Positive Gram stain or culture, particularly anaerobic organisms 1
• Anaerobic infections, which are common in aspiration pneumonia, are more likely to present with:
  • Insidious clinical onset
  • Less fever
  • Greater weight loss
  • History of possible aspiration 1

Risk Factors for Aspiration

Patients at higher risk for aspiration that may lead to pleural effusion include:

• Males (66% vs 56% in non-aspiration cases) 4
• Older adults 4
• Nursing home residents (15% vs 5.9% in non-aspiration cases) 4
• History of alcohol abuse (21% vs 8% in non-aspiration cases) 4
• Decreased level of consciousness (lower Glasgow Coma Scale) 4
• Dysphagia or impaired swallowing 5
• Compromised airway defense mechanisms 5
• Gastroesophageal reflux disease 5
• Recurrent vomiting 5

Management of Aspiration-Related Pleural Effusion

Management depends on the nature and severity of the effusion:

• Simple parapneumonic effusions (pH >7.2, LDH <1000 IU/l, no organisms) usually resolve with antibiotics alone 1
• Complicated parapneumonic effusions (pH <7.2, LDH >1000 IU/l) require chest tube drainage 1
• Frank empyema (purulent fluid) requires chest tube drainage without need for additional biochemical tests 1
• Diagnostic thoracentesis should be performed when a significant pleural effusion is present 1
• Pleural fluid should be sent for:
  • Gram stain and bacterial culture 1
  • Biochemistry (pH, protein, glucose, LDH) 1
  • Cytology to rule out malignancy 1

Outcomes and Prognosis

Aspiration-related pleural effusions can have significant consequences:

• Patients with aspiration are more likely to require mechanical ventilation (54% vs 32%) 4
• They have higher rates of moderate to severe ARDS (12% vs 3.8%) 4
• Mortality is approximately twofold higher, even after adjustment for severity of illness 4
• Appropriate and timely drainage of complicated effusions is essential to prevent loculation and organization of the effusion 1

Special Considerations

• Ultrasound is recommended to locate pleural fluid and guide aspiration 1
• CT scanning may help differentiate pleural empyema from a parenchymal lung abscess in difficult cases 1
• In patients with suspected aspiration but negative cultures, consider that prior antibiotic therapy may have sterilized the pleural fluid 1
• Anaerobic cultures should always be obtained when aspiration is suspected 1

Aspiration-related pleural effusions require prompt recognition and appropriate management to prevent complications and improve outcomes.