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- diagnostic (to determine the cause of a pleural effusion)
- therapeutic (to relieve symptoms of dyspnoea).
- Local skin infection
- Uncooperative patient
- Uncorrected bleeding diathesis – Deranged INR (ideally INR should be less than 1.5).
- Relative contraindication with bullous lung disease and small effusions
- Mark the optimal site for aspiration, on the posterolateral aspect of the chest wall (midscapular or posterior axillary line), 1–2 intercostal spaces below the percussed upper border of the effusion.
- Ensure the proposed site is directly over a palpable intercostal space and above the level of the diaphragm (no lower than the 8th intercostal space).
- Note: If the effusion is poorly defined clinically do not proceed; request USS to mark the effusion.
- Pneumothorax—Intercostal drain insertion may be necessary.
- Bleeding—Apply direct pressure.
- Spleen or liver puncture—Request an ultrasound of the chest with marking of the site for aspiration if the fluid is difficult to detect.
- Costal neurovascular bundle damage: The chances of penetrating this bundle can be minimised by always inserting the needle over the upper border of a rib
Pleural effusions – clinical assessment
There are many causes of pleural effusions and they are commonly classified into transudates and exudates
Causes of transudate pleural effusions ((protein < 30 g/L)
- Heart failure
- Peritoneal dialysis
- Nephrotic syndrome
- Mitral stenosis
Causes of exudative pleural effusions (protein > 30 g/L)
- Malignancy (most commonly lung cancer in men and breast cancer in women)
- Pulmonary embolism (80% exudates, 20% transudates)
- Autoimmune disease (especially rheumatoid arthritis)
- Asbestos exposure
- Dressler’s syndrome (following AMI)
Pleural fluid laboratory analysis
- A transudate contains less than 25 g/l of protein
- An exudate contains more than 35 g/l of protein
- If the pleural fluid contains protein at levels between 25 g/l and 35 g/l then Lights Criteria should be used to decide whether the effusion is a transudate or an exudate
- Lights criteria state that the fluid is an exudate if one or more of the following criteria are met:
- Pleural fluid : Serum protein ratio is greater than 0.5
- Pleural fluid LDH : Serum LDH is greater than 0.6
- Pleural fluid LDH is greater than two thirds the upper limit of normal serum LDH.
If exudate is confirmed, further testing required to evaluate the cause of exudate
- Differential cell count (predominance of white cells)
- Gram stain and culture and cytology
- LDH level – This is classically high in exudates
- Pleural fluid pH (Low glucose and pH = infection or malignancy)