Pleural effusions are commonly associated with pneumo- nia and should be assessed via thoracentesis to determine whether the pleural fluid is also infected. A viscous, infected pleural fluid can become organized following pneumonia, resulting in development of empyema or chronic pleural effusion with trapped lung that is unable to reexpand.
In order to prevent these complications, it is recommended that all pleural effusions separated from the chest wall by >10 mm undergo thoracentesis.
Characteristics that predict increased likelihood of complications with a parapneumonic effusion include: loculated pleural fluid, pleural fluid pH <7.20, pleural fluid glucose <60 mg/dL, positive Gram stain or culture of the pleural fluid, and presence of frank pus (em- pyema) of the pleural space.
Individuals whose pleural fluid has any of these characteristics should be considered for tube thoracostomy drainage of the pleural fluid.