RespiratoryTier 2Topic

Thoracentesis, with or without pleural ultrasound

What it is

Needle aspiration of pleural fluid - diagnostic (fluid analysis) and/or therapeutic (symptom relief from a large effusion)
Ultrasound guidance has become standard of care given a substantial reduction in complication rates (organ puncture, pneumothorax) compared with blind/landmark-based aspiration

Light's criteria

Light's criteria distinguish transudate from exudate when serum protein/LDH are also available: exudate if pleural:serum protein ratio >0.5, OR pleural:serum LDH ratio >0.6, OR pleural LDH >2/3 the upper limit of normal serum LDH

Fluid analysis

Transudate (heart failure, cirrhosis, nephrotic syndrome) - usually bilateral, treat the underlying systemic cause, drainage rarely needed unless large/symptomatic
Exudate - send for cytology (malignancy), Gram stain/culture/AFB (infection/empyema), glucose (low in empyema/malignancy/rheumatoid effusion), pH (<7.2 suggests complicated parapneumonic effusion/empyema requiring drainage, not just antibiotics)

Therapeutic aspiration and drainage

Therapeutic aspiration limited to ~1-1.5L per session to reduce re-expansion pulmonary oedema risk
A complicated parapneumonic effusion/empyema requires chest drain insertion, not repeated aspiration alone

Causes of effusion

Heart failure, malignant pleural effusion, parapneumonic effusion/empyema, tuberculous pleural effusion

Next steps

A large, recurrent, or exudative effusion of unclear cause after initial aspiration warrants further investigation (imaging, biopsy) rather than repeated drainage alone

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