American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the indication for thoracostomy tube drainage of parapneumonic pleural effusions?

1. pH greater than 7.2

2. Glucose level more than 60 mg/dL

3. pH less than 7.2 or glucose level less than 60 mg/dL

4. Symptom relief only

The correct answer is: pH less than 7.2 or glucose level less than 60 mg/dL

Thoracostomy tube drainage of parapneumonic pleural effusions is indicated when the pleural fluid analysis reveals a pH of less than 7.2 or a glucose level of less than 60 mg/dL. These parameters suggest that the effusion is likely complicated, either as an empyema or as a significant infectious process that may not adequately resolve without drainage. A pH less than 7.2 indicates a more acidic environment, which often occurs due to bacterial metabolism in an infected pleural space. A glucose level below 60 mg/dL is suggestive of more severe pleural disease and often correlates with the presence of infection. In such cases, the likelihood of spontaneous resolution of the effusion without intervention is low, making drainage necessary to prevent complications and improve patient outcomes. In contrast, a pH greater than 7.2 or a glucose level above 60 mg/dL would indicate that the effusion is less likely to be infected and may not require drainage. Symptom relief alone is not a sufficient indication for drainage; the underlying pathology of the pleural effusion must also be considered to prevent further complications.