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Breathing - Thoracentesis (effusion)


Pleural effusion

Unknown cause (diagnostic)

Impairing respiration (therapeutic)

Contraindications (absolute in bold)

Coagulopathy or thrombocytopenia (APTT >50 seconds, platelets <50, INR >1.5 or NOAC use in last 24 hours)

Loculated effusion or pleural adhesions (known or seen on bedside ultrasound)

Prior pleural space surgical intervention

Bullous disease

Positive pressure ventilation

Overlying skin infection

Uncooperative patient


Conservative management (no aspiration)

Small intercostal catheter (Seldinger technique)

Surgical drainage and pleurodesis

Informed consent

Medical emergency

Consent is not required if the patient lacks capacity or is unable to consent

Brief verbal discussion is recommended if the situation allows


Written consent

More complex non-emergency procedure with higher risk of complications

Potential complications





Neurovascular, visceral and pulmonary parenchymal damage


Re-expansion pulmonary oedema


Procedural hygiene

Standard precautions

Surgical aseptic non-touch technique

PPE: sterile gloves and gown, surgical mask, eye protection, sterile ultrasound probe cover


Monitored bed space


Procedural clinician and assistant


Ultrasound machine with low (identification) and high (guided aspiration) frequency probes

25g needle and syringe (for local anaesthetic)

21g needle and 60ml syringe (for diagnostic tap)

16-18g cannula or thoracentesis catheter if available (for therapeutic tap)

60ml syringe

Three-way tap and extension tubing

Pleural fluid collection vessel

Sterile occlusive dressing

Positioning (our preferred site is the triangle of safety)

On the bed with head elevated to 45 degrees

Arm on the side of the lesion behind the patient’s head (abducted and externally rotated)

Locate safe triangle: lateral to pectoralis major, medial to latissimus dorsi, fourth or fifth intercostal space, anterior to mid-axillary line

With the arm by the side, mark the anterior mid-arm point from shoulder tip to antecubital fossa (preferred), or

Place your open hand in the axilla and mark the edge of the hand between the anterior and mid-axillary line, or

Palpate the second intercostal space at the sternal angle, move down two spaces and palpate space around to the axilla

Ultrasound-guided site of entry: two intercostal spaces below the highest level of effusion

Mark site using ultrasound confirming 10mm of fluid thickness at chosen site noting soft tissue depth


10ml lignocaine 1% with adrenaline (1:100,000)

Supplemental oxygen throughout procedure

Sequence (diagnostic tap - effusion)

Mark site using ultrasound and measure soft tissue depth

Anaesthetise skin and proceed the over top of rib to anaesthetises soft tissue, muscle, periosteum

After aspirating pleural fluid stop advancing needle and inject final anaesthetic, then withdraw needle

Attach 21g needle to 60ml syringe and advance over the top of rib aspirating as you advance

After aspirating pleural fluid stop advancing needle and stabilise with thumb and index finger

Aspirate 50ml of fluid, then ask the patient to exhale (to prevent indrawing of air) as you remove the needle

Distribute fluid into specimen containers for diagnostic analysis

Cover insertion site with occlusive dressing

Sequence (therapeutic tap - effusion)

Mark site using ultrasound and measure soft tissue depth

Anaesthetise skin and proceed the over top of rib to anaesthetises soft tissue, muscle, periosteum

After aspirating pleural fluid stop advancing needle and inject final anaesthetic, then withdraw needle

Advance 16-18g cannula with syringe attached over the top of rib aspirating as you advance

After aspirating pleural fluid, angle the cannula caudally and insert over the needle (Seldinger technique)

Remove needle with syringe attached, leaving only plastic cannula in place and attach closed three-way tap to cannula

Attach 60ml syringe to distal three-way tap port and the extension set to the third port

Place free end of extension tubing in a container to collect the pleural fluid

Close tap to extension set and withdraw 50ml fluid into syringe

Close tap to patient and push syringe fluid through extension set into a collecting container

Distribute fluid into specimen containers for diagnostic analysis and repeat aspiration

Repeat, up to a maximum of 1.5l fluid (due to risk of re-expansion oedema)

After procedure, remove catheter as patient holds breath at end expiration

Cover insertion site with occlusive dressing

Post-procedure care

Ongoing care

Monitor for respiratory distress or haemodynamic compromise for a minimum of two hours

Provide analgesia if required

Post-aspiration chest X-ray

Discussion with respiratory physician

Document procedure (completion, complications)

Laboratory testing of sample

Cell count and differential

Gram stain and culture (aerobic and anaerobic)

Biochemical analysis (pH, protein, albumin, glucose, LDH)



Ultrasound-guided fluid aspiration increases success rates and reduces complications

Pleural aspiration with large-bore needles should be avoided due to increased risk of pneumothorax

The risk of bleeding with a small needle is low even if the patient has an uncorrected coagulopathy


We recommend the primary attempt for needle thoracentesis is a 5cm cannula placed perpendicular to the skin in the fourth or fifth intercostal space between the anterior to mid-axillary line as suggested by the British Thoracic Society guidelines. Other positions such as the midscapular line (while sitting forward) or posterior axillary line (while lying on side with effusion down) are also acceptable, provided this is above the ninth rib (two rib spaces below the tip of the scapular) to avoid abdominal visceral injury. Aspirations at the second intercostal space midclavicular line have a high failure rate (with a 5cm catheter) and are generally not recommended.

Re-expansion pulmonary oedema rarely occurs, most often unilaterally after the re-expansion of a lung that had been collapsed for longer than three days. The risk is greater with large effusions. It follows in 1% of pleural fluid aspirates >1.5 litres. It is linked to the generation of increased negative pleural pressure, which can also cause pain or cough. The procedure should therefore be terminated with the onset of cough or chest pain during aspiration fluid or after 1.5l has been drained.

Peer review

This guideline has been reviewed and approved by the following expert groups:

Emergency Care Institute

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