Indications
- Diagnostic — unilateral effusion of unknown etiology
- Diagnostic — bilateral effusions not responding to CHF therapy
- Diagnostic — suspected empyema or parapneumonic effusion
- Therapeutic — large effusion causing dyspnea
- Therapeutic — malignant effusion (palliation)
- Recurrent malignant effusion — consider PleurX catheter
- Transudates — bilateral, cardiac/hepatic/renal cause — treat underlying
- Hemothorax — large volume may require chest tube
Light's Criteria and Fluid Analysis
Light's criteria classify pleural fluid as exudate (at least one criterion met) vs transudate (none met). Exudate: pleural protein/serum protein >0.5; pleural LDH/serum LDH >0.6; pleural LDH >2/3 upper limit of normal serum LDH.
- Exudate — pneumonia, malignancy, PE, TB, rheumatoid
- Transudate — CHF, cirrhosis, nephrotic syndrome, hypoalbuminemia
- Glucose <60 — empyema, rheumatoid, malignancy, TB
- pH <7.2 — complicated parapneumonic (chest tube indicated)
- Triglycerides >110 — chylothorax (lymphatic injury)
- Cytology — low sensitivity (~60%) for malignancy
- Culture and Gram stain — essential for suspected empyema
- Hematocrit — if bloody: pleural Hct/blood Hct >0.5 = hemothorax
Full Thoracentesis Procedure Playbook
Ultrasound technique, needle and catheter selection, fluid analysis, and complication management
Technique and Complications
- US guidance — identify fluid depth, lung, diaphragm
- Sitting or lateral decubitus position
- Superior rib margin — avoid neurovascular bundle below rib
- 8th–9th intercostal space, posterior — standard access
- Pneumothorax — ~1% US-guided vs 6% landmark
- Limit to 1.5 L per session — re-expansion pulmonary edema risk
- Re-expansion pulmonary edema — dyspnea, hypoxia after large drainage
- No routine CXR — only if symptoms or air aspirated