Day #100 - Pleural Effusion/Empyema

Today we talked about the approach to pleural effusions:

1) How to do a thoracentesis

Pleural fluid can be mainly water (transudate) or exudative: blood (hemothorax), pus (empyema/complicated parapneumonic effusion), inflammatory, or chyle (chlothorax)

2) Light's Criteria for transudate vs. exudate

One of:

• Protein in pleural fluid >0.5 plasma
• LDH in pleural fluid >0.6 plasma
• LDH in pleural fluid >2/3 upper limit of normal in serum

False positive rate ~25%. Can measure SAPG (like SAAG) which if >12 suggests transudate. Do this if you had a low pre-test probablity of exudate.

This article discusses liklihood ratios for each value of these measurements and can be really helpful.

3) Management of complicated pleural effusion/empyema (great article here)

• • "The Sun Should Never Set of An Undrainded [Unsampled] Parapneumonic Effusion"
    
  • Sample the fluid at least
  • If >50% of lung has effusion, loculated, air-fluid levels, pleural thickening or pleural enhancement on CT highly suggestive that you will need drainage
  • Aspiration of frank pus, anaerobic smell, positive gram stain/culture, pH below 7.2, LDH >1000 imply you will need drainage
  • Drainage options include:
    
    • repeated thoracentesis
    • pig tail catheter (probably safer than surgical chest tube, less morbidity, but more likely to become clogged if frank pus. can also be inserted by seldinger technique with initial thoracentesis)
      
    • surgical chest tube (probably required for very thick, poorly flowing purulent material. higher morbidity than pig-tail)
      
    • VATS drainage: for failure of above, for patients with chronic empyema, ongoing sepsis, if need for decortication of "trapped lung"

Shameless self plug: here is my talk on the epidemiology of pneumococcal empyema.