Should we drain pleural effusion in mechanically ventilated patients?

Abstract

Pleural effusions are common in the critically ill patients. They are associated with an increase in the duration of mechanical ventilation and intensive care unit (ICU) length of stay, but a causal relationship cannot be ascertained. Systematic drainage of pleural effusion in mechanically ventilated patients is controversial because of lack of definitive data on the risk/benefit ratio. Large pleural effusions are associated with a significant loss of lung volume and an alteration in respiratory mechanics. After drainage, improvement in oxygenation and respiratory mechanics is inconsistent across studies. These effects may be delayed and secondary to progressive lung volume expansion, which could explain some of the discrepancies among studies. This effect is likely to be modest in patients with acute respiratory distress syndrome (ARDS). There are no randomized studies to assess the interest of pleural drainage in reducing the duration of mechanical ventilation or length of ICU stay. However, the risks of pleural drainage (pneumothorax, hemothorax) are low if the operator is trained and assisted by ultrasound. Arguments in favor of pleural drainage include a large effusion on ultrasound (endexpiratory interpleural distance ≥25 mm, predicting an effusion volume ≥500 mL), absence of ARDS, and a low risk of complications (ventilatory conditions, hemorrhagic risk).