What are the indications for pleural (lung) drainage?

Indications for Pleural Drainage

Pleural drainage is indicated for: (1) pleural infection with pH ≤7.2 or frank pus, (2) symptomatic large effusions causing respiratory compromise, (3) pneumothorax requiring intervention, and (4) malignant effusions causing dyspnea when life expectancy permits definitive management.

Pleural Infection (Parapneumonic Effusion/Empyema)

Absolute Indications

• Frank pus on thoracentesis requires immediate chest tube drainage 1
• Pleural fluid pH ≤7.2 indicates high risk of complicated parapneumonic effusion (CPPE) and mandates intercostal drain (ICD) insertion if safe volume exists on ultrasound 1
• Pleural fluid pH ≤7.15 specifically indicates high CPPE risk requiring drainage 1

Intermediate Risk Criteria

• Pleural fluid pH between 7.2-7.4 with LDH >900 IU/L should prompt ICD consideration, especially with:
  • Ongoing fever 1
  • High pleural fluid volume 1
  • Low glucose (<4.0 mmol/L or 72 mg/dL) 1
  • Pleural contrast enhancement on CT 1
  • Septations on ultrasound 1

Additional Infection-Related Indications

• Loculated pleural collections require earlier chest tube drainage 1
• Large effusions (>40% hemithorax) are more likely to require surgical intervention 1, 2
• Effusions enlarging or compromising respiratory function should not be managed by antibiotics alone 1

Important Caveats

• Pleural fluid pH >7.38 indicates very low CPPE risk and does not require immediate drainage 1
• When pH measurement unavailable, glucose <3.3 mmol/L suggests high CPPE probability 1
• Repeated thoracentesis is not recommended for significant pleural infection—insert drain at outset 1

Malignant Pleural Effusions

Symptomatic Effusions

• Drainage is indicated for symptomatic malignant effusions causing dyspnea 1
• Large-volume thoracentesis should precede definitive intervention to confirm symptom relief and assess lung expandability 1

Asymptomatic Effusions

• Therapeutic interventions should not be performed for asymptomatic malignant effusions unless diagnostic sampling is needed 1
• Draining asymptomatic effusions subjects patients to procedural risks without clinical benefit 1

Palliative Considerations

• Repeat pleural aspiration is appropriate for patients with very short life expectancy and poor performance status 1
• Intercostal tube drainage with pleurodesis achieves >60% success rate for preventing recurrence 1

Pneumothorax

• Pneumothorax requires drainage when clinical assessment combined with ultrasound findings indicate significant lung collapse or respiratory compromise 1
• Ultrasound is superior to chest X-ray for ruling out pneumothorax, with higher sensitivity 1
• The lung point location on ultrasound allows semi-quantification of lung collapse 1

Tuberculous Pleural Effusions

• Routine drainage is not recommended unless the effusion is large and symptomatic or shows evidence of complicated infection 2
• Drainage indications include:
  • Large symptomatic effusions causing respiratory distress 2
  • Frankly purulent or turbid/cloudy fluid 2
  • pH <7.2 in non-purulent but possibly infected effusions 2
  • Loculated effusions 2
• Tuberculous empyema often requires surgical drainage in addition to anti-TB chemotherapy 2

Technical Considerations

Ultrasound Guidance

• Ultrasound must be used to confirm pleural fluid presence and should guide thoracocentesis or drain placement 1
• Ultrasound reduces pneumothorax risk by 19% compared to landmark technique 1
• Ultrasound allows reliable quantification of effusion volume and identification of loculations 1

Drain Size and Placement

• Small bore percutaneous drains (10-14F) should be the initial choice for effusion drainage 1
• Drains should be inserted at the optimum site suggested by ultrasound 1
• Large bore surgical drains should be placed in the mid-axillary line through the "safe triangle" 1

Safety Requirements

• Chest drains should be inserted by adequately trained personnel with a suitable assistant and trained nurse available 1
• Routine coagulation studies only needed in patients with known risk factors 1
• Coagulopathy should be corrected before insertion when possible 1

Critical Pitfalls to Avoid

• Delaying drainage when pH ≤7.2 or frank pus is present increases morbidity and hospital stay 1, 2
• Do not contaminate pH samples with local anesthetic or heparin 1
• Consider alternative diagnoses mimicking low pH effusions (rheumatoid effusion, advanced malignancy/mesothelioma) 1
• Avoid pleurodesis attempts in patients with nonexpandable lung—use indwelling pleural catheters instead 1
• A respiratory physician or thoracic surgeon should be involved in care of all patients requiring chest tube drainage for pleural infection 1