What is the diagnosis, treatment, and management of pleural effusion in the Cardiovascular Intensive Care Unit (CVICU)?

Pleural Effusion in CVICU: Diagnosis, Signs and Symptoms, and Management

Pleural effusion in the CVICU setting requires prompt diagnosis and management, with thoracentesis recommended for effusions larger than 10 mm to determine etiology and guide appropriate treatment. 1

Definition and Pathophysiology

• Pleural effusion is defined as an abnormal accumulation of fluid in the pleural space exceeding the normal amount of 0.1 to 0.2 mL/kg body weight 1
• Common mechanisms include increased pulmonary capillary pressure, increased pleural membrane permeability, decreased oncotic pressure, or lymphatic obstruction 1
• Pleural effusions are categorized as transudative (reflecting systemic etiology) or exudative (usually from localized pleural process) 1

Prevalence in CVICU

• The prevalence of pleural effusions following cardiac surgery is high, with 42-89% of patients showing radiographic evidence of pleural effusion in the early postoperative period 1
• Approximately 6.6% of patients require intervention following coronary artery bypass grafting (CABG) or valve surgery 1
• In general ICU settings, pleural effusion prevalence varies from 8% with physical examination to over 60% when routine ultrasonography is used 2

Etiology in CVICU

• Early postoperative effusions (within 30 days) typically have higher erythrocyte, LDH, and eosinophil counts, related to surgical trauma and bleeding 1
• Late effusions (beyond 30 days) are predominantly lymphocytic with lower LDH levels, suggesting an immune-mediated response 1
• Common causes in CVICU include:
  • Postoperative fluid overload 1, 3
  • Heart failure (most common cause, accounting for 35% of ICU pleural effusions) 3
  • Atelectasis (23% of ICU pleural effusions) 3
  • Parapneumonic effusions 3
  • Surgical trauma 1
  • Chylothorax (from operative damage to thoracic duct) 1
  • Postoperative infection 1

Signs and Symptoms

• Dyspnea is the most common presenting symptom, initially on exertion 4
• Chest pain may be present, typically dull and aching rather than pleuritic 1
• Cough (predominantly dry) 4
• Tachypnea 1
• Many patients may be asymptomatic, especially with small effusions 1
• In CVICU, "clinically significant" effusions are defined by:
  • Increased respiratory support requirements 1
  • Shortness of breath 1
  • Cough 1
  • Tachypnea 1
  • Pain 1

Diagnostic Approach

Imaging

• Chest radiographs can typically detect >75 mL on lateral view and >175 mL on frontal view 1
• Thoracic ultrasound can detect >20 mL of pleural fluid and is recommended for guiding thoracentesis 1, 5
• Chest CT can detect >10 mL of pleural fluid and is considered the reference standard for imaging 1
• CT is helpful to evaluate underlying parenchymal disease, mediastinal lymph node involvement, and pleural lesions 1

Diagnostic Thoracentesis

• Recommended for new and unexplained pleural effusions 4
• Ultrasound guidance is recommended, especially if the effusion is small 5
• Pleural fluid analysis should include:
  • Appearance (clear, turbid, purulent, bloody) 5
  • Biochemistry (protein, LDH, glucose, pH) 5
  • Cell count and differential 1
  • Cytology 5
  • Microbiology (Gram stain and culture) 5
  • Amylase (if indicated) 1

Criteria for Exudate vs. Transudate

• Light's criteria to identify exudates (any one of the following):
  • Pleural fluid protein/serum protein ratio > 0.5 1
  • Pleural fluid LDH/serum LDH ratio > 0.6 1
  • Pleural fluid LDH > two-thirds the upper limit of normal serum LDH 1

Management in CVICU

General Principles

• Treatment should address the underlying cause 4
• Transudative effusions (heart failure, fluid overload) are usually managed by treating the underlying medical disorder 4
• Large or symptomatic effusions require drainage for symptomatic relief 4

Specific Management in CVICU

• For postoperative pleural effusions:

  • Protocolized intervention for symptomatic effusions with estimated volume >480 mL can reduce length of stay by 3±1.5 days compared to diuresis alone 1
  • Ultrasound-guided thoracentesis is well-tolerated and preferred over surgical tube thoracostomy as initial intervention 1
  • Caution should be taken if removing more than 1.5 L on a single occasion to avoid re-expansion pulmonary edema 1, 5

• For infected pleural effusions:

  • Purulent or turbid fluid indicates pleural infection requiring prompt chest tube drainage 5
  • Positive Gram stain or culture requires chest tube drainage and appropriate antibiotics 5
  • pH < 7.2 indicates need for chest tube drainage 5

• For malignant pleural effusions:

  • Consider chemical pleurodesis (talc has highest success rate at 93%) for recurrent effusions 5
  • Palliative drainage for symptomatic relief 5

CVICU-Specific Tips

• Monitor for pleural effusions in all post-cardiac surgery patients, as they are extremely common 1
• Consider dedicated follow-up and drainage protocols, which can enhance recovery rates by up to 15% 1
• Small effusions (maximal thickness <10 mm on ultrasound) can be observed if asymptomatic 5
• In patients with bilateral effusions, heart failure is the most common cause (38%) 3
• Patients with pleural effusions in ICU typically have:
  • Lower serum albumin concentration 3
  • Higher APACHE II scores 3
  • Longer ICU stays 3
  • Longer mechanical ventilation requirements 3
• Thoracentesis is safe in mechanically ventilated patients 2
• Pleural effusions in CVICU rarely cause death directly but contribute to morbidity and prolonged hospitalization 3