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Thoracentesis is a procedure that removes pleural fluid for diagnostic and/or therapeutic purposes. It is used to relieve symptoms (e.g., dyspnea) and/or obtain pleural fluid for analysis to help determine the underlying cause (e.g., infection, malignancy). Relative contraindications include coagulopathy and infection over the procedure site. It is important to determine the best puncture site using ultrasound guidance and ensure all necessary equipment is at the bedside before performing the procedure. Complications include and pneumothorax.
See also “Pleural effusion.”
- Absolute: None
surgery, or implantation is preferable for certain patients and underlying etiologies (see “ ” for details). with ,
We list the most important contraindications. The selection is not exhaustive.
- Low-viscosity pleural effusions: Small-bore (e.g., 8–14 Fr) thoracostomy tubes are usually appropriate. 
- High-viscosity or complicated pleural effusions (e.g., pleural empyema, hemothorax, associated pneumothorax): Larger-bore (e.g., 20–36 Fr) thoracostomy tubes are typically required (see “Chest tube placement”). 
Landmarks and positioning
- Ultrasound machine
- Sterile gown and gloves
- Surgical mask
- Sterile drapes
- Sterile ultrasound probe cover
- Antiseptic solution
- Local anesthetic (e.g., 1% lidocaine)
- 22-gauge, 2-inch needle :
- 18-gauge needle with preloaded 8 Fr catheter) : over-the-needle assembly (e.g.,
- Syringe (e.g., 60 mL for diagnostic, 10 mL for therapeutic thoracentesis)
- Occlusive dressing
- Tubes for sample collection
- Drainage setup (if indicated)
- High-pressure tubing
- Drainage bag or evacuated container
Puncture of the intrapleural space
- Administer along the anticipated needle tract.
- Assemble the appropriate needle and syringe for the procedure.
- Insert the needle at the anesthetized puncture site under ultrasound guidance.
- Maintain negative pressure on the syringe and advance until fluid returns.
- Once position is confirmed, continue with or as indicated.
- Once fluid removal is complete, withdraw the needle as the patient exhales and apply an .
Diagnostic thoracentesis steps 
- Attach the thoracentesis needle to a 60 mL syringe.
- Follow steps to .
- Once proper needle position is confirmed, collect 50 mL of pleural fluid.
Therapeutic thoracentesis steps 
- Attach the over-the-needle assembly to a 10 mL syringe.
- Follow steps to .
- Once proper needle position is confirmed, advance the catheter over the needle into the pleural space.
- Remove the needle and attach a to the catheter hub.
- Connect high-pressure tubing to the .
- Attach the tubing to a drainage bag or evacuated container.
- Allow drainage of a maximum of 1500 mL of pleural fluid.
- Stop drainage if the patient develops a cough, chest discomfort, or hypoxia. 
Avoid draining more than 1500 mL of pleural fluid, as it is associated with a higher risk of . 
Pitfalls and troubleshooting
|Pitfalls and troubleshooting during thoracentesis |
|Complication||Prevention and screening||Management|
|Vascular injury and hemothorax|| |
|Infection and empyema|| || |
|Reexpansion pulmonary edema|| || |