What are the typical thoracentesis findings in empyema?

From the Guidelines

Thoracentesis findings in empyema typically reveal purulent, thick, and foul-smelling pleural fluid, characterized by a low pH, low glucose levels, and elevated LDH levels, with a high white blood cell count and positive cultures for pathogens. The diagnosis of empyema is based on the presence of pus in the pleural space, and thoracentesis is a crucial diagnostic tool in identifying the condition 1. The fluid analysis typically shows a pH less than 7.2, glucose levels below 60 mg/dL, and elevated LDH levels greater than 1000 IU/L, indicating an exudative process 1. Some key characteristics of empyema fluid include:

• High protein levels (>3 g/dL)
• Low glucose and pH
• Elevated LDH levels
• High white blood cell count (>50,000 cells/μL) with a predominance of neutrophils
• Positive Gram stain and cultures for pathogens, such as anaerobes, Streptococcus species, or Staphylococcus aureus
• Loculations and fibrin deposition, which can make drainage difficult with a simple thoracentesis needle These findings reflect the intense inflammatory response to infection within the pleural space, where bacteria and inflammatory cells accumulate, creating a thick, purulent collection 1. The management of empyema involves drainage of the infected pleural fluid, which can be achieved through thoracentesis, chest tube drainage, or surgical intervention, depending on the severity of the condition and the presence of loculations or fibrin deposition 1. In terms of specific management decisions, the size of the effusion and the degree of respiratory compromise are important factors to consider, with small effusions often responding well to antibiotic therapy alone, while larger effusions may require drainage 1. Overall, the diagnosis and management of empyema require a comprehensive approach, including thoracentesis, fluid analysis, and appropriate antimicrobial therapy, as well as consideration of the need for drainage and other interventions to ensure optimal outcomes 1.

From the Research

Typical Thoracentesis Findings in Empyema

The typical thoracentesis findings in empyema include:

• Frankly purulent infection of the pleural space, as stated in the study 2
• Presence of pus in the pleural space, commonly due to adjacent pneumonia, chest wall injury, or a complication of thoracic surgery, as mentioned in the study 3
• Pleural effusion, which may be diagnosed using contrast-enhanced computed tomography, with a "split pleura" sign being highly suggestive in the appropriate clinical setting, as noted in the study 2

Diagnostic Thoracentesis

Diagnostic thoracentesis with culture and Gram stain is used to guide appropriate antibiotic therapy, as stated in the study 2

• The procedure involves the insertion of a needle or catheter into the pleural space to obtain a sample of the fluid for analysis
• The fluid is then sent to the laboratory for culture, Gram stain, and other tests to determine the cause of the infection

Therapeutic Drainage

Therapeutic drainage with small-bore tube thoracostomy has been shown to be a safe and effective treatment of early stage empyema, as mentioned in the study 2

• Augmentation of tube placement with intrapleural fibrinolytics and mucolytics facilitates catheter drainage by degrading loculations and decreasing fluid viscosity, respectively, as noted in the study 2
• The goal of therapeutic drainage is to remove the infected fluid from the pleural space and prevent further complications, such as lung entrapment or fibrosis, as discussed in the study 4