Thoracentesis

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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 reexpansion pulmonary edema and pneumothorax.

See also “Pleural effusion.”

• Diagnostic thoracentesis: the sampling of a pleural effusion for pleural fluid analysis and identification of the etiology ^[2]
• Therapeutic thoracentesis: removal of pleural fluid to relieve symptoms (e.g., dyspnea) and treat respiratory failure ^[2][3]

• Diagnostic thoracentesis ^[2][3]
  • New unilateral effusion of uncertain etiology
  • Bilateral effusions with atypical findings (e.g., pleuritic chest pain, fever, disparate effusion sizes)
  • Indications for detailed pleural fluid analysis that impact management (e.g., cytology, culture and sensitivity)
  • Parapneumonic effusion > 5 cm
• Therapeutic thoracentesis ^[2][3]
  • Large symptomatic pleural effusions in select patients
  • Pleural effusions causing respiratory failure and/or obstructive shock
  • Complicated parapneumonic effusion

Patients with conditions known to cause bilateral symmetrical pleural effusions (e.g., heart failure, cirrhosis, ESRD) typically do not require a confirmatory diagnostic thoracentesis.

• Absolute: None
• Relative
  • Coagulopathy
  • Infection (e.g., cellulitis, herpes zoster) over the puncture site
  • Adhesions ^[4]

Pleural fluid drainage with chest tube insertion, surgery, or indwelling pleural catheter implantation is preferable for certain patients and underlying etiologies (see “Pleural effusion treatment” for details).

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. ^[5]
• 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”). ^[3][5]

• Place the patient in the sitting position with their arms resting on the bedside table.
• Determine the puncture site using ultrasound and mark the skin.
  • 1–2 intercostal spaces beneath the upper margin of the effusion
  • Midscapular or posterior axillary line

• Obtain informed consent.
• Initiate continuous cardiac monitoring and pulse oximetry.
• Perform skin preparation and maintain a sterile field.
• Provide parenteral analgesics as needed.

• Ultrasound machine
• Sterile gown and gloves
• Surgical mask
• Sterile drapes
• Sterile ultrasound probe cover
• Antiseptic solution
• Local anesthetic (e.g., 1% lidocaine)
• Needle
  • Diagnostic thoracentesis: 22-gauge, 2-inch needle
  • Therapeutic thoracentesis: over-the-needle assembly (e.g., 18-gauge needle with preloaded 8 Fr catheter)
• Syringe (e.g., 60 mL for diagnostic, 10 mL for therapeutic thoracentesis)
• Occlusive dressing
• Tubes for sample collection
• Drainage setup (if indicated)
  • Three-way stopcock
  • High-pressure tubing
  • Drainage bag or evacuated container

Puncture of the intrapleural space

1. Administer single-point local anesthesia along the anticipated needle track.
2. Assemble the appropriate needle and syringe for the procedure.
3. Insert the needle at the anesthetized puncture site under ultrasound guidance.
4. Maintain negative pressure on the syringe and advance until fluid returns.
5. Once position is confirmed, continue with diagnostic thoracentesis steps or therapeutic thoracentesis steps as indicated.
6. Once fluid removal is complete, withdraw the needle as the patient exhales and apply an occlusive dressing.

Diagnostic thoracentesis steps ^[3]

1. Attach the thoracentesis needle to a 60 mL syringe.
2. Follow steps to puncture the intrapleural space.
3. Once proper needle position is confirmed, collect 50 mL of pleural fluid.

Therapeutic thoracentesis steps ^[3]

1. Attach the over-the-needle assembly to a 10 mL syringe.
2. Follow steps to puncture the intrapleural space.
3. Once proper needle position is confirmed, advance the catheter over the needle into the pleural space.
4. Remove the needle and attach a three-way stopcock to the catheter hub.
5. Connect high-pressure tubing to the three-way stopcock.
6. Attach the tubing to a drainage bag or evacuated container.
7. Allow drainage of a maximum of 1500 mL of pleural fluid.
8. Stop drainage if the patient develops a cough, chest discomfort, or hypoxia. ^[6]

Avoid draining more than 1500 mL of pleural fluid, as it is associated with a higher risk of reexpansion pulmonary edema. ^[3]

• Samples sent for pleural fluid analysis (if indicated)
• Serum total protein and LDH levels obtained (if indicated)
• Procedure documented
• Patients monitored for signs of reexpansion pulmonary edema

Postprocedure CXR is not routinely recommended in asymptomatic patients with uncomplicated thoracentesis. ^[8][9]

• Diagnotic thoracentesis: See “Pleural fluid analysis.”
• Therapeutic thoracentesis: See “Management of pleural effusion” for details on clinical reassessment.

• Reexpansion pulmonary edema
• Vascular injury
• Hemothorax
• Pneumothorax
• Infection (e.g., pleuritis, empyema)
• Intraabdominal injury (e.g., injury to the diaphragm, liver, and/or spleen) ^[10]

We list the most important complications. The selection is not exhaustive.