Also known as pleural fluid aspiration, the thoracic wall is punctured to obtain a specimen of pleural fluid for analysis or to relieve pulmonary compression and resultant respiratory distress. Locating the fluid before thoracentesis reduces the risk of puncturing the lung, liver, or spleen.

The pleural cavity should contain less than 20 ml of serous fluid. Pleural effusion results from the abnormal formation or reabsorption of pleural fluid. Certain characteristics classify pleural fluid as either a transudate or exudates.


  • To provide pleural fluid specimens to determine the cause and nature of pleural effusion.
  • To provide symptomatic relief with large pleural effusion.
  1. Check the patient’s history for bleeding disorders or anticoagulant therapy.
  2. Explain that a chest X-ray or ultrasound study may precede the test.
  3. Explain the procedure to the patient.
  4. Instruct the patient no to cough, breathe deeply, or move during the test to minimize the risk of lung injury.
  5. Record the patient’s baseline vital signs.
  6. Shave the area around the needle insertion site, if necessary, and position the patient properly.
  1. Position the patient to widen the intercostals spaces and allow easier access to the pleural cavity.
  2. If the patient can’t sit up, position him on his unaffected side with the arm on the affected side elevated.
  3. After the patient is in proper position, prepare and drape the site.
  4. Inject a local anesthetic into the subcutaneous tissue; the thoracenthesis needle is then inserted.
  5. When the needle reaches the pocket of fluid, it’s attached to a 50-ml syringe or a vacuum bottle and the fluid is removed.
  6. During aspiration, the patient is monitors for signs of respiratory distress and hypotension.
  7. Pleural fluid characteristics and total volume are noted.
  8. After the needle is withdrawn, apply pressure until hemostasis is obtained and a small dressing is applied.
  9. Place specimens in proper containers, labeled appropriately, and send to the laboratory immediately.
  10. Pleural fluid for pH determination must be collected anaerobically, heparinized, kept on ice, and analyzed promptly.
Nursing Interventions
  1. Elevate the head of the bed to facilitate breathing.
  2. Obtain a chest X-ray.
  3. Tell the patient to immediately report difficulty of breathing.
  4. Immediately report signs and symptoms of pneumothorax, tension pneumothorax, and pleural fluid reaccumulation.
  5. Monitor the patient for reexpansion pulmonary edema (RPE), a rare but serious complication of thoracentesis. Thoracentesis hould be halted If the patient has sudden chest tightness or coughing.
  6. Monitor vital signs, pulse oximetry, and breathe sounds.
  7. Observe the puncture site and dressings.
  8. Watch for subcutaneous emphysema.
  9. Monitor pleural pressure.
Normal Results
  • Negative pressure in the pleural cavity with less than 50 ml serous fluid.
Abnormal Results
  • Bloody fluid suggests possible hemothorax, malignancy, and traumatic tap.
  • Milky fluid suggests chylothorax.
  • Fluid with pus suggests empyema.
  • Transudative effusion suggests heart failure, hepatic cirrhosis, or renal disease.
  • Exudative effusion, suggests lymphatic drainage abstraction, infections, pulmonary infarctions, and neoplasma.
  • Positive cultures suggest infection.
  • Predominating lymphocytes suggest tuberculosis or fungal or viral effusions.
  • Pleural fluid glucose levels that are 30 to 40 mg/dl lower than blood glucose levels may indicate cancer, bacterial infection, or metastasis.
  • Increased amylase suggests pleural effusions associated with pancreatitis.
Interfering Factors
  • Failure to use sterile technique.
  • Antimicrobial therapy before fluid aspiration for culture (possible decrease in numbers of bacteria, making it difficult to isolate the infecting organism).
  • Thoracentesis is contraindicated in the patient who has a history of bleeding disorders or anticoagulant therapy.
  • The strict sterile technique.
  • Laceration of intercostals vessels
  • Pneumothorax
  • Mediastinal shift
  • Reexpansion pulmonary edema (RPE)
  • Bleeding and infection