Pleural Effusions

  • The pleural space normally contains a minimal amount of fluid. A pleural effusion is an excessive collection of fluid in the pleural space resulting from an underlying disease process (see Table 3F.1).
  • Effusions may be transudative (resulting from changes in hydrostatic or oncotic pressure) or exudative (secondary to alterations in capillary permeability or lymphatic/ vascular obstruction).
Diagnosis

  • Patients with small effusions are often asymptomatic. Common complaints with symptomatic effusions are dyspnea, pleurisy chest pain, or cough. Patients may also have complaints related to their underlying disease or give a history of cancer, heart failure, or other co morbidity.

    Table Causes of pleural effusions
    Transudative Congestive heart failure
    Nephritic syndrome
    Renal failure
    Cirrhosis
    Pulmonary embolism
    Exudative Pulmonary infections
    Pulmonary embolism
    Malignancy (primary or metastatic)
    Drug induced effusion
    Connective tissue disease
    Trauma
    Sub diaphragmatic abscess
    Esophageal perforation
    Pancreatitis

  • The physician should note any increased work of breathing or obvious respiratory distress. Pulmonary exam may also reveal decreased breath sounds, dullness to percussion, and decreased tactile fremitus. A friction rub is sometimes noted with medium-sized effusions. Extra pulmonary findings are present depending upon the etiology and include peripheral edema, jugular venous distension, ascites, abdominal tenderness, and lymphadenopathy among others.
  • Diagnostic Studies
  • CXR-As little as 175 ml is visualized as a blunting of the costophrenic angle on a routine film. A lateral decubitus view can identify even smaller amounts of fluid.
    Subpulmonic effusions appear as an elevated hemi diaphragm.
  • Laboratory-Selected studies often include a CBC, electrolytes, BUN, creatinine, and glucose depending upon the suspected etiology. If a thoracentesis will be preformed, additional tests should include a serum protein and lactate dehydrogenase (LDH).
  • Thoracentesis
  • Classification of pleural effusions as a transudate includes a ratio of pleural fluid protein to serum protein < 0.5, pleural fluid LDH < 200 IU/ml, a ratio of pleural fluid LDH to serum LDH < 0.6, fluid protein < 3 g/100 ml, and fluid pH < 1.016.
    Effusions that exceed these values are classified as exudates.
  • Other tests to consider for exudative pleural fluid are cell count and differential, pH, glucose, Gram stain, bacterial culture, and cytology. Consider amylase if pancreatitis or esophageal rupture is suspected.

Treatment

  • Initial treatment includes oxygenation, and ventilatory and circulatory support if needed.
    Large effusions causing respiratory compromise require emergent drainage.
  • Patients with effusions should have a diagnostic thoracentesis unless the etiology is apparent (heart failure, pneumonia, etc). It has been recommended that no more than 1,000-1,500 ml is drained at one time in order to prevent reexpansion pulmonary edema. This complication is rare and is minimized by the avoidance of excessive negative pressure.
  • Specific treatments are based on the underlying cause of the effusion as determined by clinical presentation and diagnostic thoracentesis.
  • Chest tube placement is required for empyema and hemothorax.

Disposition

  • The need for hospital admission is based on the degree of respiratory or circulatory impairment, as well as the cause of the effusion. Most patients are admitted to the hospital following a thoracentesis for observation and treatment of the underlying condition.
  • In a minority of cases, well-appearing patients can be discharged home after thoracentesis following 4-6 h of observation. All patients who have had a thoracentesis must have a post-procedure CXR to rule out complications such as pneumothorax or hemothorax.

Suggested Reading

  1. Berkman N, Kramer MR. Diagnostic tests in pleural effusion-an update. Postgrad Med J 1993; 69:12-8.
  2. Heffner JE. Evaluating diagnostic tests in the pleural space. Differentiating transudates from exudates as a model. Clin Chest Med 1998; 19:277-93.
  3. Light RW. Useful tests on the pleural fluid in the management of patients with pleural effusions. Curr Opin Pulm Med 1999; 5:245-9.
  4. Strange C. Pleural complications in the intensive care unit. Clin Chest Med. 1999; 20:317-27.
  5. Ross DS. Thoracentesis. In: Roberts JR, Hedges JR, eds. Clinical Procedures in Emergency Medicine, 2nd ed. WB Saunders Company, 1991.
       
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