Flashcards in Respiratory - Pleural effusion & pneumothorax Deck (25):
What is a pleural effusion?
This is a collection of fluid in the pleural space. If the effusion is infected it is called an empyema. If it relates to pneumonia it is called a para-pneumonic effusion.
What is the pathogenesis of pleural effusion?
Pleural effusion is a common problem. The normal parietal pleura produces fluid which is reabsorbed by the visceral pleura. Either excessive fluid production (e.g. as a result of inflammation) or impaired re-absorption leads to accumulation of fluid. An effusion needs to be a moderate size at least before it produces symptoms of shortness of breath.
What are the clinical features of a pleural effusion?
The most common presentation is SOB. Pleural inflammation may cause pain and large effusions may cause cough.
The clinical signs are reduced expansion, stony dullness and reduced breath sounds and vocal resonance.
Effusions <500ml are difficult to detect clinically. The chest X ray will show blunting of the costophrenic angle in small collections and more extensive change in the presence of larger effusions. Large effusions are more commonly the result of malignancy.
How should pleural effusions be investigated?
The main distinction in determining the cause of an effusion is between high and low protein content - i.e. exudates vs transudates.
If pleural infection is suspected, the pH of the fluid should be measured (pH < 7.2 suggests complicated para pneumonic effusion or empyema which will only resolve with pleural drainage). Fluid should also be sent for biochemistry (LDH) - high in rheumatoid effusions and exudates, protein, and MC&S.
What are transudative effusions?
This is accumulation of fluid with a low protein and low LDH content within the pleural space. Specifically protein should be < 30g/dL. They are often BILATERAL.
What is the aetiology of transudative effusions?
1) Increased hydrostatic pressure: CCF, constrictive pericarditis, pericardial effusion
2) Decreased capillary osmotic pressure: cirrhosis, nephrotic syndrome, malnutrition
3) Extension from peritoneum: any cause of ascites, peritoneal dialysis
More common causes: cardiac failure, nephrotic syndrome, hepatic cirrhosis, hypoalbuminaemia (malnutrition, chronic disease, malabsorption)
Less common causes: pericardial constriction, Meig syndrome (ovarian fibroma associated with right sided effusion), myxoedema
What is the colour of a transudative effusion?
Usually clear, or straw coloured and serous. Contains occasional lymphoctyes and mesothelial cells.
What is an exudative effusion?
An accumulation of protein-rich fluid in the pleural space from leakage of capillaries. The protein is >30g/dL (or pleural/ serum protein ratio >0.5) and LDH is high at >200u. These are often UNILATERAL.
What are the causes of exudative pleural effusions?
1) Neoplasms: metastatic spread to pleura, mesothelioma
2) Infections: pneumonia, abscess, TB, subphrenic abscess
3) Immune disorders; postmyocardial infarct, rheumatoid disease, SLE, WGs
4) Pulmonary infarction
5) Other causes: radiation therapy, asbestos exposure, drug reactions, pancreatitis, uraemia
More common causes: baterial pneumonia, carcinoma, mesothelioma
Less common causes: TB, haemothorax, pancreatitis, sub-phrenic abscess, autoimmune disease, chylothorax (from a leaking thoracic duct [trauma, neoplasia] - only left sided), Yellow nail syndrome (abnormal lymph drainage, leading to yellow nails, pleural effusion and lymphoedema)
What is the appearance of exudative effusions?
They can be serous (TB, RA), cloudy (infection), bloody (cancer, PE, TB).
In para-pneumonic effusions if pH is <7.2 high probability the effusion is infected (empyema).
What is Light's criteria?
If the effusion protein is between 25-35g/L then Light's criteria can be applied to determine whether the effusion is transudative or exudative. A pleural fluid protein/ serum protein ratio of >0.5 suggests the effusion is exudative.
How should pleural effusions be managed?
Treat the underlying cause, particularly for transudates:
- therapeutic large volume aspiration will improve symptoms. Formal drainage with intercostal tubes is often necessary with large effusions
- in non malignant and other recurrent effusion, agents (generally iodized talc) can be introduced via an intercostal drain to stick the two layers of pleura together and prevent reaccumulation (pleurodesis)
- Thoracoscopy (under local or general) may be useful in some patients to provide access to the pleura for guided biopsies and subsequent pleurodesis
What is en empyema?
This is pus within the pleural cavity
What causes empyema?
1) Pulmonary infection: empyema is most commonly a complication of intrapulmonary infection, e.g. pneumonia, TB, lung abscess
2) Other infections: spread from subphrenic abscess, acute mediastinitis and distant infective foci
3) Surgery/ trauma: as a complication of thoracic surgery or penetrating chest wall injury
What organisms most commonly caused empyema?
Mixed aerobic and anaerobic organisms are common.
Gram positive organisms, e.g. Strep. pneumoniae or Staph aureus are common causes of empyema complicating pulmonary parenchymal infection. Empyema secondary to surgery, trauma or oesophageal disease is usually due to gram negatives.
What are the consequences of empyema?
1) Toxaemia: systemic effects of infection
2) Lung collapse: compression of the lung with impaired lung function
3) Bronchopleural fistula: infection ruptures into the airways and pleura resulting in fistulous communication
4) Pleural scarring: if the empyema is evacuated or early resolution occurs, the fibrin/ granulation tissue on the pleural surface organizes with fibrous adhesions between the visceral and parietal layers. If more long standing, there is increased deposition of granulation tissue which heals with extensive dense pleural fibrosis or obliteration of the pleural cavity. This results in permanent encasement of the underlying lung
What is a pneumothorax?
This is free air in the pleural space
What is the aetiology of pneumothorax?
1) Primary spontaneous pneumothorax: implies normal underlying lungs and is caused by rupture of a pleural "bleb"
2) Secondary spontaneous pneumothorax: occurs in association with lung disease (e.g. COPD, pneumonia etc). Rupture of the visceral pleura results in communication between the airway and the pleural space
What determines the effect of a pneumothorax?
The effects of a pneumothorax depend on whether the pleural leak persists or not:
1) "Closed" pneumothorax: the leak closes are the lung deflates so the amount of air escaping into the pleural space is limited, pleural pressure remains negative and slow resolution will occur even without treatment
2) "Open" pneumothorax: occurs when persistent communication between the airway and the pleural space develops (e.g. bronchopleural fistula), seen as persistent bubbling of the chest drain. The lung cannot re expand and there is increased risk of infection developing by transmission of organisms via the airway into the pleural space
What is a tension pneumothorax?
This occurs when the leak remains open but acts as a one way valve between the airway and pleural space. Progressive increase in the volume of gas in the pleural space leads to an increase in pressure above atmospheric and compression of the underlying and contralateral lung and the heart and mediastinal shift. Cardiac filling and output decrease as the patient can become extremely unwell and die!
What are the clinical features of pneumothoraces?
Small pneumothorax may be asymptomatic
Medium/ large pneumothorax: sudden onset of chest pain with shortness of breath is the most common presentation. There is hyperinflation with reduced expansion and reduced breath sounds.
What investigations are used in pneumothorax?
- CXR is diagnostic. Mediastinal deviation suggests the presence of tension. The X ray will show the presence of any underlying lung disease
- Oxygen saturation: should be measured - usually normal unless there is underlying lung disease
- Ultrasound or CT: are both better than plain CXR for detection of small pneumothoraces and are often used after percutaneous lung biopsy
How should pneumothorax be managed?
The main treatment options are therapeutic aspiration or intercostal drainage.
For small, asymptomatic primary spontaneous pneumothoraces patients can safely be reviewed in outpatient clinic.
For symptomatic primary or secondary pneumothoraces patients are first trialed with percutaneous aspiration. If this does not resolve the pneumothorax or there is a small residual left over then patients should have an intercostal drain inserted.
All patients with underlying lung disease (even if not symptomatic) should be monitored as an inpatient because they have an increased risk of complications.
When should surgical treatment be offered for pneumothoraces?
Surgical treatment, with pleural abrasion or pleurectomy to obliterate the pleural space, is often used for non resolving pneumothoraces after tube drainage and for recurrent pneumothoraces.