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Pleural Effusion and Empyema

Pleural Effusion: Definition and Anatomic Alterations

  • Definition: Excess accumulation of fluid in the pleural space that separates the visceral and parietal pleura and compresses the lungs.
  • Anatomic alterations of the lungs due to effusion:
    • Lung compression
    • Atelectasis
    • Compression of the great veins and decreased cardiac venous return
  • Imaging/figures indicate right-sided effusion with fluid accumulation (FA), depressed diaphragm (DD), and partially collapsed lung (CL); atelectasis is a common secondary alteration.

Etiology and Epidemiology

  • Affects approximately 1.3 million people each year in the U.S.
  • Early signs include chest pressure, dyspnea, and cough.
  • Chest pressure does not typically develop until the effusion is in the moderate to large range:
    • Moderate: 500 ext{ mL} o 1500 ext{ mL}
    • Large: >1500 ext{ mL}
  • Dyspnea is rare in small effusions.
  • Cough is related to the degree of atelectasis.
  • Pleural effusions may be transudative or exudative.

Pleural Fluids: Transudative vs Exudative

Transudative Pleural Effusion

  • Mechanism: Transudate develops when fluid from pulmonary capillaries moves into the pleural space.
  • Fluid characteristics: Thin and watery, containing few blood cells and little protein; pleural surfaces are not involved in producing the transudate.
  • Protein/LDH: Low protein, Low LDH relative to serum; not rich in cellular debris.

Common Causes of Transudative Pleural Effusion

  • Congestive heart failure (most common)
    • Left-sided heart failure more likely than right to produce pleural effusion
  • Hepatic hydrothorax (in liver cirrhosis with ascites; ascites passes from peritoneal space to pleural space)
  • Peritoneal dialysis
  • Nephrotic syndrome
    • Effusion is generally bilateral; due to decreased plasma oncotic pressure
  • Pulmonary embolism or infarction — 30–50% develop pleural effusions
    • Obstruction of pulmonary vessels can lead to right heart failure and pleural effusion
    • Increased capillary permeability in visceral pleura can develop after ischemic infarction

Hepatic Hydrothorax with Pleural Effusion

  • Occurs in patients with liver cirrhosis.
  • Ascitic fluid trans-diffuses or migrates through the diaphragm into the pleural space.
  • Pleural effusions are commonly right-sided; may be seen with hepatic hydrothorax.

Exudative Pleural Effusion

  • Mechanism: Exudate develops due to diseased pleural surfaces (inflammation, infection, or malignancy).
  • Fluid characteristics: High protein content and a large amount of cellular debris.
  • Laboratory criteria:
    • Pleural fluid protein > 2.9 ext{ g/dL}
    • Pleural fluid cholesterol > 45 ext{ mg/dL}
    • Pleural fluid LDH > 60% of the upper limit for serum

Common Causes of Exudative Pleural Effusion

  • Malignant pleural effusions: two-thirds occur in women; highly associated with breast cancer
  • Malignant mesotheliomas (from asbestos exposure)
  • Bacterial pneumonias: ~40% have pleural effusion; most resolve, but ~10% require therapeutic intervention; untreated can progress to empyema
  • Tuberculosis (may extend from caseous tubercle into pleural cavity)
  • Fungal infections (Histoplasmosis, Coccidioidomycosis, Blastomycosis)
  • Diseases of the GI tract (e.g., pancreatitis)
  • Collagen vascular diseases (e.g., rheumatoid arthritis, Sjögren’s syndrome)

Empyema, Other Types of Effusions

  • Empyema: pus in the pleural space due to inflammation
  • Chylothorax: presence of chyle in the pleural space; caused by trauma to neck or thorax
    • Chyle: milky, white lymphatic fluid produced from dietary fats in the small intestine; transported via the thoracic duct to the neck and then to venous circulation
  • Hemothorax: blood in the pleural space; usually due to penetrating or blunt chest trauma
    • If no trauma or surgery, may indicate malignant disease; pleural fluid hematocrit is typically ≥ 50%

Other Types of Effusions

  • Distinction: Transudate vs Exudate (reiterated): transudates are from hydrostatic/is oncotic pressure imbalances; exudates result from pleural surface disease (inflammation, infection, malignancy).

Pleural Effusion: Clinical Manifestations and Exam Findings

  • Vital signs: Increased respiratory rate (RR), heart rate (HR), and sometimes blood pressure (BP) due to stress and hypoxemia
  • Chest pain and decreased chest expansion
  • Cyanosis in more advanced disease
  • Cough: usually dry and nonproductive
  • Chest exam findings:
    • Tracheal shift toward the side of the effusion if large
    • Decreased tactile fremitus and vocal fremitus
    • Dull percussion note
    • Diminished breath sounds
    • Possible displaced heart sounds
    • Pleural friction rub may be present occasionally

Pulmonary Function Test Findings (Pleural Effusion)

  • Pattern: Moderate to severe (restrictive lung pathophysiology)
  • Lung Volume and Capacity findings tendency:
    • Decreased tidal volume (VT)
    • Decreased inspiratory reserve (IRV)
    • Decreased expiratory reserve (ERV)
    • Decreased residual volume (RV)
    • Decreased vital capacity (VC)
    • Decreased inspiratory capacity (IC)
    • Decreased functional residual capacity (FRC)
    • Decreased total lung capacity (TLC)
    • RV/TLC ratio affected (generally reduced due to overall restriction)

Arterial Blood Gases (ABG) in Pleural Effusion

  • Small pleural effusion:
    • Acute alveolar hyperventilation with hypoxemia (acute respiratory alkalosis)
    • Typical ABG pattern: respiratory alkalosis with hypoxemia; pH elevated, PaCO2 decreased, HCO3- may be reduced (compensation), PaO2 reduced; SaO2/SpO2 decreased
  • Large pleural effusion:
    • Acute ventilatory failure with hypoxemia (acute respiratory acidosis) due to hypoventilation and poor gas exchange
    • ABG pattern: acidemia with increased PaCO2 and decreased HCO3-; PaO2 decreased; SaO2/SpO2 decreased

Pleural Effusion Imaging: Chest Radiography Findings

  • CXR findings in pleural effusion:
    • Blunting of the costophrenic angle
    • Fluid level on the affected side
    • Depressed diaphragms
    • Mediastinal shift may be to the unaffected side in large effusions
    • Atelectasis
    • Meniscus sign indicating fluid meniscus along the lateral border
  • Figures illustrate right-sided effusion with complications (e.g., pneumothorax in a mixed case)
  • Subpulmonic effusion: fluid collects below the lung with a characteristic meniscus and fissural signs

Grading of Pleural Effusion (Radiographic)

  • A simple classification diagram shows:
    • A: Mild
    • B: Moderate
    • C: Severe
  • Grading assists in assessing severity and planning intervention

Pleural Effusion: Diagnosis and Initial Interventions

  • Thoracentesis (diagnostic and/or therapeutic):
    • Procedure to remove fluid from the space between the pleura and chest wall
    • Performed after local anesthesia
    • Fluid is aspirated and sent to the laboratory for analysis
  • Indications for thoracentesis include diagnostic clarification and relief of symptoms in symptomatic effusions
  • Pleural fluid analysis helps distinguish transudate vs exudate and guides management

Thoracostomy and Chest Tube Insertion

  • Thoracostomy (chest tube) insertion:
    • Typically placed in the 4th or 5th intercostal space at the midaxillary line
    • Common sizes: No. 28 to No. 36 French gauge thoracostomy tubes for adults
  • Purpose: drain fluid, air, or both; facilitate re-expansion of the lung and allow healing

Pleural Fluid Management and Procedures

  • Management is individualized and aims to treat the underlying cause and relieve symptoms
  • Therapeutic strategies include:
    • If heart failure or infection is treated effectively, the effusion often resolves
    • Infection or cancer-related effusions may require chest tube drainage for several days
    • Pleurodesis: adhesion of pleural layers to obliterate the pleural space and prevent recurrent effusions or pneumothorax
    • Pleurodesis is often considered for recurrent malignant effusions or persistent effusions despite drainage

Pleural Effusion Treatment Principles

  • Treat the underlying cause (e.g., manage heart failure, treat lung infection, control cancer)
  • Consider thoracentesis for symptomatic relief and diagnostic evaluation
  • Use chest tube drainage for ongoing or complicated effusions (e.g., empyema, malignant effusions with drainage)
  • Pleurodesis to prevent recurrence in select cases

Respiratory Care Protocols (Post-Intervention)

  • Oxygen therapy protocol: titrate oxygen to maintain adequate oxygenation
  • Lung expansion therapy: emphasize strategies to promote lung re-expansion after fluid removal; include incentive spirometry and mobilization as appropriate
  • Mechanical ventilation: used in cases of respiratory failure or severe hypoxemia/hypercapnia; protocol-oriented management follows standard MV guidelines
  • The above protocols are designed to optimize gas exchange, enhance lung re-expansion, and facilitate recovery after pleural effusion treatment