Pleural Effusion Aspiration

Synonym: thoracentesis, pleural tap

This article should be read in conjunction with the separate article entitled 'Pleural Effusion'.

Percutaneous pleural effusion aspiration is carried out:

• To investigate the cause of pleural effusion: the British Thoracic Society guidelines suggest that pleural aspiration should be reserved for the investigation of unilateral exudative pleural effusions. It should not be carried out if a unilateral or bilateral transudative effusion is suspected, unless there are atypical features or failure of response to therapy.¹
• As symptom relief for breathlessness: repeated 'tapping' of fluid may be useful in palliative care. However, there is a high recurrence rate if pleurodesis (intrapleural instillation of a sclerosant) is not carried out simultaneously.²

• Very small volume of fluid
• Bleeding diathesis
• Anticoagulant therapy
• Mechanical ventilation (increased likelihood of tension pneumothorax or bronchopleural fistula if lung is punctured)
• Cutaneous disease over the proposed skin puncture site

• Can be performed in the clinic or by the bedside.
• Radiological guidance (e.g. ultrasound) is sometimes needed for smaller effusions.
• Sit the patient as upright as possible. A pillow can be used to support arms and head on an adjustable table or couch. If the patient leans forward too much it increases the risk of liver/spleen injury.
• Use an aseptic technique throughout the procedure.
• Use percussion to determine the upper level of fluid.
• The conventional site for aspiration is posteriorly, approximately 10cm lateral to the spine (mid-scapular line) and 1-2 intercostal spaces below the upper level of the fluid.
• Mark the spot and clean the area using antiseptic.
• Use local anaesthetic (5-10 ml of 1% lidocaine) to infiltrate the skin and underlying tissues. A 25G needle can be used for this.
• Avoid the intercostal nerves and vessels that run immediately beneath the rib by inserting the needle just above the upper border of the rib below your mark.
• You can confirm the correct location for pleural aspiration by aspirating a small amount of fluid through this smaller needle.
• Attach a 21G needle to a 50 ml syringe.
• Again, avoid the intercostal nerves and vessels by inserting the needle just above the upper border of the rib below your mark. Aspirate while you are advancing the needle.
• 50-100 ml of fluid is usually adequate for diagnostic purposes.
• Look at the fluid obtained and note any odour: purulent fluid suggests empyema; milky, opalescent fluid suggests chylothorax; grossly bloody fluid suggests haemothorax; anaerobic infection has a pungent odour.
• Separate the pleural fluid into different sterile pots to be sent for biochemistry, microbiology, cytology ± immunology. Some fluid should also be added to blood culture bottles.
• A post-procedure chest X-ray to look for pneumothorax is not generally needed provided the patient is asymptomatic and the procedure was uncomplicated.

If the procedure is being carried out to relieve breathlessness, a greater volume of fluid usually needs to be drained:⁵

• Use a 14G intravenous cannula instead of the 21G needle.
• Administer oxygen and use pulse oximetry throughout the procedure.
• Follow the same steps as above.
• When the cannula is inserted, remove the stylet and connect a closed pleural aspiration kit.
• The fluid should still be sent for analysis.
• It is best to remove fluid slowly.
• Monitor for chest pressure or pain during fluid removal. This can be a sign of lung entrapment due to extensive pleural involvement or endobronchial obstruction which will prevent re-expansion of the lung when the fluid is removed. If this occurs, stop the procedure.³
• Rarely, if more than 1.5 litres of fluid is drained off, fluid shifts can cause haemodynamic instability or pulmonary oedema. The recommended fluid drainage limit is 1-1.5 litres.

A chest drain can also be inserted for pleural fluid drainage.

The British Thoracic Society suggest the following initial investigations:

• Microbiology:
  • Send 1 pot for Gram stain, AAFB stain, microscopy, culture and sensitivity.
  • Send some fluid in blood culture bottles (increases yield, especially for anaerobic organisms).⁶
• Biochemistry:
  • Send 1 pot for protein, lactate dehydrogenase (LDH) and pH.
• Cytology:
  • Send a 20 ml sample in a sterile pot for cytological examination. Some cytologists prefer samples to be sent in a citrate bottle to prevent clots (discuss with your laboratory).
  • Sample needs to be fresh. It can be stored at 4°C for up to 4 days.
  • Malignant effusions can be diagnosed by pleural fluid cytology alone in 60% of cases.¹ A second sample can increase diagnostic yield.

Additional investigations should be requested under specific circumstances:¹

• If empyema is suspected send some fluid for centrifuge.
• If chylothorax is suspected send some fluid for centrifuge, cholesterol and triglyceride levels and investigation for the presence of cholesterol crystals and chylomicrons.
• If haemothorax is suspected, or the pleural fluid is grossly bloody, send some fluid for haematocrit level.
• If rheumatoid disease is suspected send some fluid for glucose and complement levels.
• If pancreatitis is suspected send some fluid for amylase level.

The interpretation of pleural fluid results is discussed in the separate article 'Pleural Effusion'.

• Pain during and after procedure at puncture site
• Pneumothorax (complicates 12-30% of pleural aspirations but chest drain treatment is required in <5% of these)
• Bleeding (may be cutaneous or internal)
• Empyema
• Inadvertent liver/spleen puncture