Pleural Effusions


Background

Around 60% of ICU patients have a pleural effusion on x-ray. The actual incidence will be much greater as it requires >150 mls of fluid to be visible on CXR. Ultrasound is much more sensitive and specific. See lung ultrasound - pleural effusion for more info.

Symptoms

Pleuritic chest pain SOB Cough – non-productive

Signs

↓ AE
Dull PN
↓ tactile fremitus
Rub
↓ compliance
Hypoxia

Investigations

Restrictive defect with ↓ FRC CXR

  • Opacified bases with blunting costophrenic angles.
  • No air bronchograms.
  • Supine – generalized haziness of affected side with still visible vascular markings.
  • Compete whiteout if large – shift to opposite side distinguishes it from collapse.
US - see Lung Ultrasound
CT

Transudates
Diseases that affect the filtration of pleural fluid
  • CCF
  • ↓ protein – cirrhosis, hypoalbuminaemia
  • Peritoneal dialysis
Exudates Inflammation or injury increases epithelial permeability to protein and other cells.
  • Infection – pneumonia, subphrenic abscess
  • PE
  • Malignancy
  • Pancreatitis
  • Collagen vascular diseases
  • Oesophageal perforation
Tests
Exudates (at least 1 of following) 98% sens; 85% spec Ratio of pleural fluid protein to serum protein >0.5 Ratio of pleural fluid LDH to serum LDH >0.6 Pleural fluid LDH >2/3 normal upper limit for serum.
Transudates none of above Send for Microscopy, Culture and Sensitivity LDH - >1000 suggests empyema Protein
Cytology (malignancy) pH
  • Normally 7.6.
  • Low pH suggests infection.
  • If <7.2 and parapneumonic associated with bad outcome.
  • Can use an ABG machine for testing if in a heparinized syringe and not turbid.
  • No need to test pH if turbid as a drain is indicated anyway.
Other tests: AFB (if TB suspected), glucose, amylase.

Empyema

Mortality 20%
20% require surgery
Progression of parapneumonic effusion to empyema:
1. Parapneumonic effusion - free flowing exudate with normal pH.
2. Complicated parapneumonic effusion - Clear fluid with pH <7.2.
3. Empyema – frank pus
2 and 3 are a fibropululent phase with possible septations (seen on US much better than CT). Proliferation of bacteria causes the decrease in pH. This may progress to organized fibrous material.
Ongoing sepsis after 3 days (BTS guidance) or failure of CRP to reduce by 50% in patients with pneumonia should raise the suspicion of pleural infection.
It should also be suspected in any patient with sepsis and an effusion without any other obvious source.
Management is drainage and antibiotics.

Bacteria

Strep species 50%
Anaerobes 35% on culture but 75% in DNA amplification.
Staph species and gram –ves make up the rest.
Broad spectrum antibiotic cover is therefore required until organisms and sensitivities are known. Co-amoxyclav, piperacillin-tazobactam and meropenem would all give appropriate cover as would a combination of a 2nd or 3rd generation cephalosporin and metronidazole. Gentamycin does not cover anaerobes and more importantly poorly penetrates the pleura so should not be used.

Management of an effusion

Tap if: Associated with pneumonia. Large. Suspicion of an exudate.
Drain if: Cloudy fluid Infected fluid pH <7.2
Loculated Large effusion (>1L) compromising respiration Haemothorax
  • Early drainage
  • Clotted blood cannot be drained and can get infected or cause mechanical compromise
  • Initial drainage of 1500mls or >200mls/h is an indication for surgery
The NPSA and BTS both recommend using ultrasound guidance for all pleural procedures. There is evidence that the incidence of pneumothorax is reduced from 10 to 1% with ultrasound. Safety of ultrasound-guided thoracentesis in patients receiving mechanical ventilation. Chest 2004;125: 1059–62. Safety of thoracentesis in mechanically ventilated patients. Chest 1993; 103: 1920–1.
Drainage of simple effusions is best done with a 14-16G cannula unless very viscous or blood. If a drain is used small seldinger drains are more comfortable for the patient.
Evidence shows no benefit of larger drains and that they are more painful. The relationship between chest tube size and clinical outcome in pleural infection. Chest 2010;137: 536–43. Fibrinolytics are often used in pleural infection to break down loculations and prevent tube blockage from fibrin rich fluid. One study NEJM 2005 showed no benefit but did not differentiate between loculated and simple effusions. The BTS recommend them if loculated effusions are resistant to drainage and surgery is not going to happen.
Tube should be 3cm under water. Respiratory swing confirms pleural placement and tube patency. Blocked tubes can be flushed with 50mls saline. Max 1.5 litres should be drained at any one time or 500 mls/h to avoid re-expansion pulmonary oedema.

Removal of drains

Haemothorax – when it completely ceases to drain.
Transudates – when it reduces to insignificant quantities (<100mls in 24h). Clamping of the drain before removal is unnecessary. The chest tube should be removed either while the patient performs a Valsalva’s manoeuvre or during expiration. A brisk firm movement is required with an assistant tying the previously placed closure suture.

Surgery

Pleural infections should have resolved 5-8 days after drainage and ABX. Purulent fluid and loculations make surgical intervention more likely. Failure of sepsis to resolve and a persistent collection after 5-7 days is an indication for surgical referral (BTS guidance).
The surgical options include:
  • Rib resection and drainage.
  • VATS
  • Open thoracotomy and decortication.
The latter 2 require 1 lung ventilation although respiratory physicians in other countries are perfoming VATS under LA and sedation.
Decortication can cause significant bleeding and air leaks.
Considerations for anaesthesia include:
  • Is there and air leak (BPF)?
  • Is one lung ventilation needed?
  • What are the options for analgesia?
I recommend the CEACCP article ‘Pus in the thorax’ for further elaboration of these points.

Re-expansion pulmonary oedema

Occurs after rapid evacuation of a large effusion or decompression of a spontaneous pneumothorax. Due to increased capillary permeability and hydrostatic pressure. Drain no more than 1.5L at any one time or drain at <500 mls/h.