Pleural Effusion Flashcards
What is a pleural effusion?
What is the difference between this, an empyema and haemothorax?
pleural effusion is the accumulation of fluid within the pleural space
empyema is a collection of pus within the pleural cavity
haemothorax is a collection of blood within the pleural cavity
What does a clear, a yellow and a bloody pleural fluid sample tell you about the possible cause of illness?
Straw coloured / clear:
- transudate / exudate
Yellow / white , foul smelling:
- empyema / parapneumonic effusion
Blood:
- trauma, malignancy, pulmonary infarct
What are the clinical features of pleural effusion?
- reduced chest expansion on affected side
- mediastinal displacement away from the affected side
- stony dull to percussion
- reduced or absent breath sounds
- reduced or absent vocal resonance
Why are clinical features not always present in patients with a pleural effusion?
these will generally only be present when the effusion is greater than 500ml
What size does an effusion need to be to be seen on chest X-ray?
an effusion of less than 300ml may not be seen on x-ray
an effusion of less than 500ml is unlikely to cause anything other than blunting of the costophrenic recess
>500ml will cause a clear fluid level
What do you need to look for when trying to identify a pneumothorax on CXR?
look for the meniscus
this is likely to be a very long curve, perhaps rising all the way to the axilla
if the fluid level appears perfectly horizontal, it is likely to be due to co-existing pneumothorax
If a pleural effusion is very large, what may it look like on CXR?
What can fluid below the lung be confused for?
if the effusion is large enough, the whole of one lung field may appear opaque
the mediastinum may be shifted to the opposite side
fluid below the lung can simulate a raised hemidiaphragm
Where is a needle inserted when performing a diagnositic aspiration?
How much fluid should be taken?
- percuss the upper border of the effusion, then go 1-2 intercostal spaces below
- use 5-10ml of lideocaine and inject down to the pleura
- insert a 21G needle with syringe just above the ribs upper border (to avoid the neurovascular border)
- take 10-30ml of fluid
Where should the fluid collected from diagnostic aspiration be sent?
- clinical biochemistry for presence fo glucose, protein, pH, amylase, LDH
- bacteria culture
- cytology
- immunology
If diagnosis is not possible from fluid sampling, what should be done?
diagnosis may be possible with a pleural biopsy
this should be CT guided for the best results
What should be looked for on bloods in a suspected pleural effusion?
- protein - to check for hypoalbuminaemia
- glucose - to compare to the pleural fluid sample
- LFTs
- U&Es - to check for renal failure
What are exudates?
What is the protein content?
fluids that have left the circulatory system and gone into lesions or areas of inflammation
they are defined by having a protein content >35g/L
What are the contents of an exudate like?
the composition varies, but it can include pretty much anything that is in blood
it will nearly always have water and dissolved solutes
it may also have WBCs, RBCs and platelets
exudates have a high protein content
What are transudates?
What is the protein content?
transudates are caused by disturbances in oncotic pressure (i.e. increases in venous pressure), and not by inflammation
they are defined by a protein content of <25 g/L
What is the composition of transudates like?
they typically have a lower protein content, and will contain fewer cells
the fluid typically only contains mononuclear cells, such as macrophages and lymphocytes
What is the difference in the way in which a transudate and exudate is formed?
a transudate is caused by a high pressure forcing plasma and some blood products out of the blood across a membrane
an exudate is formed by the leaking of fluid from one space to another
Why is glucose measured in suspected pleural effusion?
a low glucose content in relation to the patient’s current blood glucose indicates the presence of cells (possibly native or foreign) in the fluid
this can indicate the presence of infection
Why is pH measured when diagnosing pleural effusion?
a pH of <7.2 suggests empyema (exudate)
Why is amylase measured when diagnosing pleural effusion?
raised amylase may indicate carcinoma, pancreatic disease or an oesophageal rupture
In practice, what is used to determine the difference between a transudate and an exudate?
Why can it be difficult to tell them apart?
transudates often appear more “clear” than exudates but it is difficult to tell them apart when protein is 25 - 35 g/L
Light’s criteria is used to differentiate them
According to Light’s criteria, when is a fluid an exudate?
A fluid is an exudate if:
- [pleural protein : serum protein] > 0.5
- [pleural LDH : serum LDH] > 0.6
- pleural LDH > 200
How is pleural effusion managed if there is clear evidence of a transudative cause?
!!! DO NOT DRAIN THE EFFUSION !!!
If there is clear evidence of a transudative cause, the underlying cause should be treated without draining the effusion
e.g. LVF, renal failure, hypoalbuminaemia
If you are unsure about what is causing a pleural effusion, what procedure should be performed?
PLEURAL TAP (thoracocentesis)
this is not the same as a chest drain, which often stays in place for several days
this just aspirates a sample of fluid
this fluid is then sent for cytology, LDH, protein, pH, Gram stain and AFB testing
(AFB = acid fast bacilli - TB)
What bloods should be sent at the same time as pleural tap?
- LDH
- glucose
- CRP and ESR
- albumin
- amylase
If pleural effusion has an exudative cause, how is it treated?
- the underlying disorder needs to be treated
- the effusion should be drained as necessary
this may mean draining the effusion many times
Why does fluid need to be removed from a pleural effusion slowly?
large, fast fluid changes can lead to pulmonary oedema
maximum of 2L can be removed every 24 hours
What methods can be used to remove fluid from a pleural effusion?
needle aspiration (same method as diagnosis) or chest drain
aspiration is typically used for empyema and haemothorax
no more than 1L should be drained at a time using this method
What treatment is considered for draining a pleural effusion in malignancy and why?
pleurodesis or long-term in-dwelling chest drain
this is because most cases will recur within one month
pleurectomy may be used in some circumstances
What is pleurodesis?
the pleural space is removed and the 2 layers of pleura are stuck together, either chemically or surgically
this prevents the accumulation of fluid
chemical pleurodesis is useful in cases of recurrent pleural effusion
What agents are used in chemical pleurodesis?
- tetracycline
- talc
- bleomycin
pleurodesis talc is most useful in effusions caused by malignancy
