Pleural effusions:

  • Develop when pleural fluid formation exceeds pleural fluid absorption

  • Fluid enters the pleural space from capillaries in parietal pleura

  • Fluid is removed by the lymphatics in the parietal pleura

  • Fluid can also enter from the interstitial spaces of the lung by the visceral pleura or from peritoneal cavity through small holes in the diaphragm

  • Lymphatics can absorb 20x more fluid than is normally formed; therefore, a pleural effusion may develop when there is excess fluid formation or decreased lymphatic removal of fluid

 

 

Transudative vs. Exudative:
 

Transudative pleural effusions occur when systemic factors that influence the formation and absorption of pleural fluid are altered

Leading causes of transudative effusions:

  • LV failure

  • Nephrotic syndrome

  • Cirrhosis

  • Pulmonary emboli
    (less commonly, SVC syndrome, peritoneal dialysis, pericardial disease)

 

Exudative effusions occur when local factors that influence the formation and absorption of pleural fluid are altered

Leading causes of exudative effusions:

  • Bacterial pneumonias

  • Malignancy

  • Viral infection

  • PE
    ( also     includes large differential---Collagen-vascular diseases, uremia, Esoph perf/pancreatic dx, etc)

 

 

Exudative effusions meet at least one of the following criteria (transudative meet none):

  1. Pleural fluid protein/serum protein > 0.5

  2. Pleural fluid LDH/serum LDH > 0.6

  3. Pleural fluid LDH more than 2/3 the upper normal limit for serum

 

Parapneumonic effusion is any effusion assoc. with bacterial pneumonia, lung abscess or bronchiectasis.

A complicated parapneumonic effusion refers to those effusions which require chest tube placement for their resolution.  Empyema is pus in the pleural space, and this term is reserved for effusions on which the gram stain of the fluid is +.

 

Any one of the following  is indication for tube thoracostomy in pts with parapneumonic effusion:

  1. The presence of gross pus in the pleural space

  2. Organisms visible on gram stain of the pleural fluid

  3. Pleural fluid glucose level of < 50 mg/dl

  4. Pleural fluid ph below 7.1-7.2

 

There should be no delay in CT placement b/c a free-flowing effusion can become loculated in a matter of hours.

 

 

 

L. Keating

1/02