15 - Pleural Diseases Flashcards
What are the functions of the pleural space?
- lubrication
- prevent large collections of fluid
- evacuate gas (diffuses from pleura to capillaries along pressure gradient)
- pull the lungs against the thoracic wall
What is transudate? How is it caused?
plasma ultrafiltrate
due to altered Starling forces
- increased pleural hydrostatic force
- decreased pleural oncotic force
What is exudate? How is it caused?
protein-rich fluid
results from increased capillary leakage secondary to inflammation or disease of the pleural surface
How can you differentiate between transudate and exudate based on pleural fluid characteristics?
Exudate is diagnosed by the presence of one or more of the following:
- pleural fluid protein ÷ serum protein > 0.5
- pleural fluid LDH (lactate dehydrogenase) ÷ serum LDH > 0.6
- pleural fluid protein > 2.9 g/dL
- serum to pleural fluid albumin gradient < 1.2 g/dL
- pleural fluid cholesterol > 45 mg/dL
What are the principal causes of transudative effusion? How are they caused?
- congestive heart failure –> fluid back up from heart (systemic HTN or RV failure affects parietal hydrostatic pressure; pulmonary venous HTN or LV failure affects visceral hydrostatic pressure)
- hepatic problems –> increased fluid in parietal space
- nephrotic syndrome –> changed oncotic pressure
- atelectasis –> pulls pleura in, creating an increased negative pressure inside the pleural space
What are the principal causes of exudative effusion? How are they caused?
- inflammation or tumors (within pleural space)
- pneumonia –> bacteria across pleura
- tuberculosis
- pulmonary embolism
- collagen vascular disease
- other: chylothorax, trauma, hemothorax, pancreatitis, asbestos, drug-induced, splenic infarct
Usually caused by lymphatic obstruction, hypoplasia, or destruction
How do you treat a pleural effusion?
- determine if it’s exudative or transudative through a thoracentesis
- if transudate with symptoms –> may benefit from therapeutic thoracentesis; treat underlying cause
- if exudate –> need drainage to prevent further disease
- if malignant effusion –> pleurodesis (if not chemosensitive) or indwelling catheter (if chemosensitive)
- if hemothorax –> drain
What treatment option should be used for someone with a malignant pleural effusion?
Malignant pleural effusion indicates advanced disease, which suggests palliative therapy
- repeated thoracentesis if fluid re-accumulates slowly
- chemical pleurodesis (sclerosing agent into pleural space to minimize space available for effusion)
- indwelling catheter (at home = increased QOL)
What are the clinical characteristics of a pneumothorax?
acute onset of pleuritic chest pain and dyspnea
What are the types of pneumothorax?
- simple: due to rupture of subpleural blebs; most common in tall young men
- secondary (complicated): occurs in patients with underlying disease (most commonly COPD)
- traumatic: penetrating chest wounds or rib fractures
- iatrogenic: probably most common
How do you treat a pneumothorax?
- if small –> observation
- if large –> drainage or catheter aspiration
Parietal pleural arterial blood comes from [systemic/pulmonary] vessels. Parietal pleural venous blood drains into [systemic/pulmonary] vessels.
Visceral pleural arterial blood comes from [systemic/pulmonary] vessels. Visceral pleural venous blood drains into [systemic/pulmonary] vessels.
Parietal pleura
systemic arteries –> arterial blood
venous blood –> systemic veins
Visceral pleura
systemic arteries –> arterial blood (bronchial arteries)
venous blood –> pulmonary veins
Where is parietal lymphatic drainage located? What role does it play in clearance?
Where is visceral lymphatic drainage located? What role does it play in clearance?
Parietal
- stoma = openings between mesothelial cells (communicate pleural space with pleural lymphatics)
- clearance of protein, cells, and large particles
Visceral
- abundant lymph drainage, towards the hila
- no role in clearance
What is the innervation of the parietal and visceral pleura? Where is pain referred?
Parietal
- costal and peripheral pleura innervated by intercostal nerves (pain referred to chest wall)
- central pleura innervated by phrenic nerve (pain referred to ipsilateral shoulder)
Visceral - no sensory innervation
How is a pleural effusion formed? Where does most of the liquid come from? Why? Where does it drain?
Formed when fluid accumulation > fluid clearance
Fluid comes from both the parietal and visceral pleura, but mostly from the parietal pleura because it has a much stronger driving pressure
Fluid is cleared via the lymphatic stoma in the parietal pleura
