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Pleural aspiration (thoracocentesis)

Pleural aspiration (also known as thoracocentesis) is the aspiration of fluid from the pleural space (pleural effusion). All pleural procedures should be performed under real-time ultrasound guidance

Indications for pleural aspiration (thoracocentesis)

  • To aid the diagnosis of a unilateral, suspected exudative pleural effusion
  • To exclude empyema as this requires urgent intercostal drainage


 Equipment required for pleural aspiration (thoracocentesis)

  • Ultrasound machine and an operator who is at least level one competent at pleural ultrasound
  • Sterile ultrasound probe cover
  • Sterile gloves
  • Sterile field and dressing
  • Chlorhexidine cleaning solution
  • Lignocaine
    • Remember 3mg/kg is the maximum safe dose
      • 5mls of 2% preparation contains 100mg lignoicaine. The max dose for a 70kg person is therefore approximately 10mls 2% lignocaine.
  • 50ml syringe and green needle


 Contraindications to pleural aspiration (thoracocentesis)

  • Coagulopathy
  • Lack of ultrasound support
  • Local infection
  • Very small fluid volume



  • Consent the patient
    • Ideally written consent should be gained
    • Consent for pain, bleeding, infection, damage to surrounding structures (including pneumothorax with subsequent drain) and failure.
  • Review chest x-ray and examine patient to confirm side of insertion
  • Set up an aseptic trolley with equipment
  • Perform a provisional ultrasound


 Procedure for pleural aspiration (thoracocentesis)

  • Don sterile gloves
  • Clean the area identified for aspiration and apply a sterile field
  • Further ultrasound can be conducted with the probe in a sterile sheath
  • Infiltrate 5-10ml of lignocaine initially under the skin and then into the subcutaneous tissue and then pleural space
    • Start with an orange needle, then a blue needle and then green.
  • You should be able to access the pleural space with the green needle
  • Allow time for lignocaine to act
  • Using a green needle and 50ml syringe insert the needle along the tract used for the local anaesthetic. Aspirate as you insert the needle until fluid is aspirated.
  • Aspirate 10-30ml of fluid
  • Withdraw needle
  • Dress insertion area with a sterile dressing


Training video on the use of ultrasound in pleural aspiration


 Post-procedure care:

  • Analgesia if required.
  • Send fluid for:
    • Cytology, MC&S, LDH, Protein
    • pH (put some fluid in an ABG syringe and run through the ANG machine if necessary)
    • Consider TB culture (acid-fast bacilli) if clinically indicated
    • Consider glucose or cholesterol (if concerned about chylothorax)
  • Send serum blood samples for LDH and protein.
  • Post procedure chest x-ray to ensure no pneumothorax.
  • Ensure nursing staff are aware procedure has occurred do they can monitor more regularly.


 In the event of failure of pleural aspiration (thoracocentesis)

  • Stop procedure.
  • Seek senior help.
  • Re-review imaging and patient with a senior colleague to ensure presence of fluid.
  • Consider further imaging or aspiration in radiology.


 Top tips for pleural aspiration (thoracocentesis)

  • Send the largest sample to cytology
    • The more fluid that the lab receive the higher the diagnostic yield.
  • Explain that is a pneumothorax does occur that the patient will then require a chest drain.
  • If you diagnose an empyema on fluid pH (pH < 7.2) you must arrange for an intercostal chest drain to be inserted immediately.


Click here to download free teaching notes on pleural aspiration: Prodecures – Pleural aspiration

Perfect revision for medical students, finals, OSCEs and MRCP PACES