Pleural disease in the ICU

Contents

Overview

Pleural disease in the ICU encompasses pleural effusions (transudates and exudates), pneumothorax, haemothorax, and empyema. These conditions are both common and consequential — impairing respiratory mechanics, causing ventilatory failure, and requiring prompt diagnosis and intervention. The ICU environment complicates diagnosis (supine patients, impaired clinical examination, ventilator pressure artefacts) and demands familiarity with bedside drainage techniques and ultrasound-guided procedures.

Pleural Effusion

Pleural effusions are present in up to 60% of ICU patients. They impair gas exchange by causing compressive atelectasis and reducing functional residual capacity.

Classification: Light's Criteria

Exudate vs transudate is determined by Light's criteria (if any criterion is met, the fluid is an exudate):

  1. Pleural fluid protein / serum protein >0.5
  2. Pleural fluid LDH / serum LDH >0.6
  3. Pleural fluid LDH > 2/3 upper limit of normal serum LDH

Causes in ICU

Transudates (low protein, no active pleural inflammation):

  • Heart failure (most common)
  • Hepatic hydrothorax (usually right-sided; ascitic fluid tracking through diaphragm)
  • Hypoalbuminaemia
  • Nephrotic syndrome

Exudates (protein-rich, active pleural process):

  • Parapneumonic effusion and empyema
  • Malignancy
  • Pulmonary embolism (common, often small haemorrhagic exudate)
  • Post-cardiac surgery (Dressler-like syndrome)
  • Pancreatitis (left-sided exudate)
  • Chylothorax (milky fluid, triglycerides >1.1 mmol/L)
  • Haemothorax (trauma, iatrogenic)

Diagnosis

Chest X-ray: blunting of costophrenic angle on erect film (usually >200 mL). Supine ICU patients show haziness across the lower zone (loss of clear costophrenic angles; increased density over the lung base).

Ultrasound: The preferred modality in ICU. More sensitive than CXR, particularly for small effusions and in the supine patient. Shows anechoic (dark) fluid; allows assessment of volume and identification of loculations; guides drainage.

CT chest: Defines anatomy, identifies loculated collections, characterises the underlying lung and pleural surfaces.

Pleural fluid analysis: pH, protein, LDH, glucose, microbiology (including AFB and culture), cytology. A pleural fluid pH <7.2 in the context of a parapneumonic effusion indicates a complex effusion requiring drainage.

Management

Small asymptomatic effusions can be observed. Clinically significant effusions causing respiratory compromise, haemodynamic effects (mediastinal shift), or suspected empyema should be drained.

For transudates, treating the underlying cause (diuretics for heart failure, albumin for hypoalbuminaemia) may resolve the effusion without drainage. Large symptomatic transudates can be drained therapeutically.

Pneumothorax

Pneumothorax (PTX) is air in the pleural space. In the ICU, it may be primary (no underlying lung disease), secondary (complicating underlying disease), or iatrogenic (central venous access, intercostal nerve block, thoracentesis, barotrauma from mechanical ventilation).

Barotrauma and Ventilator-Induced PTX

Mechanical ventilation — particularly with high PEEP, high tidal volumes, or in non-homogeneous lungs (ARDS) — can cause alveolar rupture, leading to pulmonary interstitial emphysema, pneumomediastinum, pneumopericardium, or pneumothorax. Subcutaneous emphysema (crepitus over neck/chest) may be the first sign.

Diagnosis

Chest X-ray: Visible pleural line with absent lung markings beyond it; tracheal and mediastinal deviation away from the PTX if tension. Subtle findings in supine patients: deep sulcus sign (abnormally sharp costophrenic angle on the affected side), increased clarity of the medial diaphragm.

Ultrasound: Loss of lung sliding and absence of B-lines at the affected side. M-mode shows the "stratosphere sign" (absence of sandy pattern) replacing the normal "seashore sign" (lung sliding visible on M-mode). High sensitivity for PTX.

Management

Small primary PTX: Observation; 100% oxygen accelerates reabsorption (nitrogen washed out).

Significant PTX or mechanically ventilated patient: Drainage is mandatory. Any pneumothorax in a patient on positive pressure ventilation has the potential to rapidly expand to tension — drain promptly.

Intercostal drain: Second intercostal space, midclavicular line (emergency), or fourth/fifth ICS, mid-axillary line (definitive drain). Seldinger technique or surgical technique.

Tension Pneumothorax

Tension pneumothorax (tension PTX) is a life-threatening emergency. A one-way valve effect allows air into the pleural space with each inspiration but prevents its escape. Progressive ipsilateral lung collapse and mediastinal shift compress the contralateral lung and great veins, reducing venous return, cardiac output, and causing haemodynamic collapse.

Clinical features: Respiratory distress, tracheal deviation away from the affected side, absent breath sounds ipsilaterally, distended neck veins, hypotension, tachycardia. In a mechanically ventilated patient: sudden rise in peak airway pressures, haemodynamic collapse, fall in SpO2.

Diagnosis is clinical: Do not delay treatment to obtain imaging if tension PTX is suspected and the patient is deteriorating.

Management: Immediate needle decompression — large-bore cannula (14G) inserted in the second ICS, midclavicular line. A rush of air confirms the diagnosis. This is a temporising measure; an intercostal drain must follow immediately. In a crashing patient, some clinicians proceed directly to finger thoracostomy (blunt dissection through the chest wall at the fourth/fifth ICS, anterior axillary line) particularly in trauma.

Empyema

Empyema is pus in the pleural space. It arises from:

  • Complicated parapneumonic effusion (extension of pneumonia)
  • Post-operative (thoracic or oesophageal surgery)
  • Haematogenous seeding
  • Post-thoracocentesis infection (rare)

Stages

  1. Exudative: Thin, free-flowing fluid. Pleural fluid pH >7.2. Often resolves with antibiotics alone.
  2. Fibrinopurulent: Fibrin deposition, early loculation. Fluid pH <7.2, LDH rising, glucose falling. Requires drainage.
  3. Organised: Thick fibrous pleural peel trapping the lung. Requires surgery (VATS decortication or open thoracotomy).

Management

Antibiotics: Broad-spectrum empirical cover (co-amoxiclav or piperacillin-tazobactam; add metronidazole if abdominal source; vancomycin if MRSA risk). Culture guides de-escalation.

Drainage: Intercostal drain (large-bore preferred) for fibrinopurulent and established empyema. Image-guided placement (ultrasound or CT) improves accuracy, particularly for loculated collections.

Intrapleural fibrinolytics: tPA 10 mg + DNase 5 mg instilled twice daily via the chest drain for 3 days (the MIST2 trial: Maskell et al., NEJM 2011) reduces the need for surgery. tPA lyses fibrin; DNase reduces viscosity of purulent fluid. Combined therapy is superior to either alone.

Surgery: VATS decortication for stage 3 empyema or when drainage fails. Aims to remove the fibrous peel and allow lung re-expansion.

Pleural Drainage Techniques

Intercostal Drain (Chest Drain)

Site:

  • Emergency (tension PTX): 2nd ICS, midclavicular line
  • Definitive: 4th or 5th ICS, anterior to mid-axillary line (the "triangle of safety" — anterior border latissimus dorsi, lateral border pectoralis major, line above 5th ICS)

Technique options:

  • Seldinger technique: needle → wire → dilator → drain. Preferred for smaller drains (12–16 Fr) used for simple effusions and pneumothorax.
  • Blunt dissection (surgical technique): incision → blunt dissection through intercostal muscles → finger sweep → large-bore drain. Used for haemothorax, empyema, and emergencies.

Size:

  • Small-bore (12–16 Fr): sufficient for transudates, free-flowing exudates, simple PTX
  • Large-bore (24–32 Fr): haemothorax, empyema, viscous fluid

Ultrasound guidance: Recommended for all non-emergency pleural procedures. Reduces complications and improves accuracy.

Thoracentesis

Needle aspiration of pleural fluid for diagnostic sampling or therapeutic drainage of small volumes. Use 21G needle with a three-way tap. Ultrasound guidance is mandatory.

Viva Questions

How do you diagnose and manage tension pneumothorax in a mechanically ventilated patient?

Tension pneumothorax in a ventilated patient typically presents with sudden deterioration: rising peak airway pressures, fall in tidal volume delivery, haemodynamic collapse (hypotension, tachycardia), and falling SpO2. The clinical signs — absent breath sounds on the affected side, tracheal deviation away from the affected side, and distended neck veins — may be subtle or masked by positive pressure ventilation and the ICU environment. The diagnosis is clinical and must not be delayed for imaging if the patient is haemodynamically compromised. Immediate needle decompression is performed with a large-bore cannula (14G) at the second intercostal space, midclavicular line. A hiss of escaping air confirms the diagnosis and is immediately therapeutic. This is temporising — an intercostal drain must be inserted without delay on the same side. If there is diagnostic uncertainty and the patient is stable enough to tolerate it, chest ultrasound (absence of lung sliding) or CXR can guide the diagnosis. In the trauma setting, finger thoracostomy at the fourth/fifth ICS anterior axillary line may be preferred as a faster definitive decompression technique.

What is the role of intrapleural fibrinolytics in empyema and what is the evidence?

Intrapleural fibrinolytics are used in stage 2 (fibrinopurulent) empyema to break down fibrin loculations, reduce viscosity of infected pleural fluid, and improve drainage without recourse to surgery. The MIST2 trial (Rahman et al., NEJM 2011) randomised 210 patients with pleural infection to four groups: tPA + DNase, tPA alone, DNase alone, or placebo. The combination of tPA 10 mg plus DNase 5 mg instilled twice daily for three days significantly reduced the need for surgical referral and hospital length of stay. Neither agent alone was superior to placebo in this trial, suggesting that both components are necessary — tPA lyses fibrin and opens loculations, while DNase reduces the viscosity of pus (which is otherwise too thick to drain even through broken-down loculations). Current BTS guidelines recommend the combination of tPA and DNase for patients with complicated pleural infection who require drainage. Contraindications include a bronchopleural fistula (risk of systemic thrombolysis via the airway).

How do you use pleural ultrasound in the ICU and what findings would you expect with different pathologies?

Bedside pleural ultrasound is the recommended first-line imaging modality for pleural disease in ICU patients, avoiding radiation and providing real-time guidance for procedures. In normal lung, the pleural line is visible as a bright white hyperechoic line. Lung sliding — movement of the visceral pleura against the parietal pleura with respiration — is seen as a "shimmering" at the pleural line. B-lines (comet-tail artefacts) originating from the pleural line represent thickened interlobular septa or alveolar fluid and are normal in small numbers. A pleural effusion appears as an anechoic (dark) space between the visceral and parietal pleura, with the collapsed lung within it appearing as a hyperechoic structure (hepatisation). Loculations appear as echogenic septae within the effusion. Pneumothorax is identified by the absence of lung sliding and the absence of B-lines; M-mode shows the "stratosphere sign" (parallel lines throughout) rather than the normal "seashore sign" (granular pattern below the pleural line). Ultrasound can also identify A-lines in pneumothorax — horizontal artefacts parallel to the pleural line. Lung consolidation produces "hepatisation" — the lung takes on the echogenicity of the liver, with air bronchograms (bright flashes within) visible in some cases.