What is the preferred irrigation solution for intrapleural infections, saline or gentamicin with saline?

Saline Irrigation for Intrapleural Infections

Saline irrigation alone (without gentamicin) is the appropriate choice for intrapleural infections when TPA/DNase therapy or surgery is not suitable. Gentamicin should be avoided in the pleural space due to poor penetration and inactivation in acidic pleural fluid 1, 2.

Key Recommendation from Current Guidelines

The 2023 British Thoracic Society guidelines explicitly state that saline irrigation can be considered for treatment of pleural infection when intrapleural TPA and DNase therapy or surgery is not suitable 1. This represents a conditional recommendation based on evidence showing saline irrigation (250 mL three times daily) may reduce the need for thoracic surgery, though it does not impact mortality, length of hospital stay, or time to fever resolution 1.

Why Gentamicin Should Not Be Used Intrapleurally

Aminoglycosides, including gentamicin, should be avoided for intrapleural use because they:

• Have poor penetration into the pleural space 1, 2
• Become inactive in the presence of pleural fluid acidosis 1, 2
• Are not recommended by any major guideline for direct intrapleural administration 1, 2

The British Thoracic Society explicitly states that aminoglycosides should be avoided due to these pharmacological limitations 1, 2.

Practical Application of Saline Irrigation

When using saline irrigation for pleural infection:

• Volume and frequency: Use 250 mL saline three times daily through the chest tube 1
• Indication: Consider when TPA/DNase therapy is contraindicated (e.g., bleeding risk) or surgery is not feasible 1
• Mechanism: Helps maintain chest tube patency and may facilitate drainage of loculated collections 1
• Monitoring: If drainage ceases, flush with 20-50 mL normal saline to ensure tube patency 1

Evidence Supporting Saline Irrigation

Recent research demonstrates that saline irrigation is both safe and potentially beneficial:

• A 2017 study showed that manual saline flushing plus urokinase reduced fibrinolytic doses needed, chest tube duration (2 vs 5 days), and hospital stay (6 vs 8 days) compared to fibrinolytics alone, with no adverse events 3
• A 2021 cohort study of 30 patients (including those with cancer) showed a 13.3% failure rate at 3 months with saline lavage, with no chest tube blockages reported 4
• Historical data from 1981 showed irrigation eradicated infection in 5 of 6 empyema patients with shorter hospital stays compared to conventional methods 5

Treatment Algorithm for Pleural Infection

First-line approach:

1. Small-bore chest tube (≤14F) drainage plus appropriate systemic antibiotics 1
2. If drainage ceases but residual collection remains, use TPA/DNase (10 mg TPA + 5 mg DNase twice daily for 3 days) 1

When TPA/DNase or surgery not suitable: 3. Consider saline irrigation (250 mL three times daily) 1 4. Never add gentamicin or other aminoglycosides to irrigation solution 1, 2

Surgical referral if:

• Persistent sepsis despite chest tube drainage and antibiotics 1
• Failure of medical therapy including fibrinolytics 1

Critical Pitfalls to Avoid

• Do not use gentamicin intrapleurally - it is ineffective due to poor penetration and acid inactivation 1, 2
• Do not use saline irrigation as first-line therapy - it is reserved for when TPA/DNase or surgery are not options 1
• Do not add antibiotics to saline irrigation - systemic antibiotics with good pleural penetration (beta-lactams) are preferred 1, 2
• Ensure chest tube patency by regular flushing with small volumes (20-50 mL) of saline if drainage decreases 1