American Board of Internal Medicine (ABIM) Certification Practice Exam

When should a thoracostomy tube be considered for complicated pleural effusions?

1. pH is less than 7.2

2. Glucose is greater than 60 mg/dL

3. Patient is asymptomatic

4. Severe obstruction on CT

The correct answer is: pH is less than 7.2

A thoracostomy tube should be considered for complicated pleural effusions particularly when the pH of the pleural fluid is less than 7.2. This low pH indicates that the pleural effusion is likely infected or has a complex composition that can lead to the development of empyema. Such circumstances typically represent a significant pathological condition, prompting the need for drainage to relieve symptoms and prevent further complications like lung encapsulation or thickening of the pleura. The thresholds for pH and other laboratory values are critical in evaluating pleural effusions. A pH below 7.2 often suggests that the effusion is complex, meaning it could be the result of infections such as pneumonia leading to parapneumonic effusion or empyema. In these cases, a closed thoracostomy is necessary to provide adequate drainage and encourage resolution of the infection or process leading to the effusion. Other values, such as glucose levels over 60 mg/dL, could indicate a less complicated effusion, typically associated with transudative causes rather than complicated infections. In addition, if a patient is asymptomatic, the clinical decision to perform a thoracostomy tube placement is usually not warranted. Similarly, while severe