How can you differentiate transudative versus exudative pleural effusions, and what nursing actions are required when thoracentesis is performed?

• A. Exudate shows Light's criteria abnormalities (pleural/serum protein ratio >0.5 or pleural/serum LDH ratio >0.6); Transudate due to heart failure, cirrhosis, nephrotic syndrome. Post-thoracentesis: monitor vitals, oxygenation, puncture site, watch for pneumothorax and bleeding.
• B. Transudate is due to infection; exudate is due to fluid overload.
• C. Thoracentesis requires no monitoring after procedure.
• D. Light's criteria are not used to differentiate.

Answer: (A)

Differentiating pleural effusions relies on Light's criteria. An exudate is suggested when the pleural fluid protein/serum protein ratio is greater than 0.5 or the pleural fluid LDH/serum LDH ratio is greater than 0.6 (and typically with higher pleural LDH). If these thresholds aren’t met, the effusion is usually a transudate. Transudates come from systemic conditions that disturb fluid balance, such as heart failure, cirrhosis, or nephrotic syndrome, while exudates reflect inflammation, infection, malignancy, or pulmonary embolism.

When thoracentesis is performed, the nurse’s actions focus on safety and early detection of complications. Monitor vital signs and oxygen saturation before, during, and after the procedure to catch any respiratory or circulatory instability. Check the puncture site for bleeding, hematoma, or signs of infection, and apply a sterile dressing. Be vigilant for pneumothorax and monitor the patient for changes in breath sounds, sudden chest pain, or worsening dyspnea; post-procedure imaging is often done to confirm there is no pneumothorax. Provide comfort measures, assist with positioning and breathing exercises, and document the amount and appearance of drained fluid along with any complications.