Empyema thoracis

Posted by e-Medical PPT
Empyema thoracis: This develops as frank pus accumulates in the pleural space. Laboratory studies indicate that preexisting pleural fluid is required for the development of an empyema because empyema is not seen after direct inoculation into a "dry" pleural space. The pus is seen after thoracentesis or any drainage procedure of the pleural space and is generally characterized as thick, viscous, and opaque.

Causative organisms
Staphylococcus aureus, Streptococcus pneumoniae and Streptococcus pyogenes
Pneumococcal pneumonia presents with effusion in 40% patients, empyema occurs only in 5%
Anaerobes and enterobacter are common in mixed infections. Anaerobes are more common after 6 years of age. For anaerobes, aspiration pneumonia is the most common cause followed by lung abscess, sub diaphrag-matic abscess and spreading infection from adjacent sites, e.g. periodontal, retropharyn-geal, peritonsillar and neck abscesses.

Stages of Empyema
Exudative stage (1-3 days)
  • Immediate response with outpouring of the fluid.
  • Low cellular content
  • It is simple parapneumonic effusion with normal pH and glucose levels.
  • pH more than 7.30
  • glucose more than 60 mg/dl
  • pleural fluid/serum glucose ratio more than 0.5
  • LDH less than 1000 IU/L
  • Gram stain and culture is negative for micro-organism.

Fibrino purulent stage (4 to 14 days)
  • Large number of poly-morphonuclear leukocytes and fibrin accumulates
  • Fluid pH and glucose level fall while LDH rises.
  • Acumulation of neutro-phils and fibrin, effusion becomes purulent and viscous leading to development of empyema.
  • There is progressive tendency towards loculations and formation of a limiting membranes.
  • Pleural fluid analysis
  • Purulent fluid or pH less than 7.10, glucose less than 40 mg/dl and LDH more than 1000 IU/L. Gram stain and culture reports show microorganism.

Organizing stage (after 14 days)
  • Fibro-blasts grow into exudates on both the visceral and parietal pleural surfaces
  • Development of an inelastic membrane "the peel".
  • Thickened pleural peel may prevent the entry of anti-microbial drugs in the pleural space and in some cases can lead to drug resistance.
  • Most common in S. aureus infection.
  • Thickened pleural peel can restrict lung movement and it is commonly termed as trapped lung

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