Patient Care: Before the procedure, the patient is carefully examined, a history is taken, and radiological studies, such as chest x-rays or ultrasonograms, are reviewed. The procedure should be explained to the patient and sensation information provided (stinging with anesthesia instillation). The risks (bleeding, puncture of the lung with subsequent lung collapse, or introduction of infection), as well as the benefits and alternatives to the procedure, should be carefully reviewed. If the patient wishes to proceed, a consent form with the patient's signature must be completed. Allergies to local anesthetics are noted. Baseline vital signs will be obtained and supplemental oxygen administered. Cardiac monitoring is usually performed. A nurse or respiratory therapist may assist the physician and support the patient throughout the procedure. Equipment is assembled for the procedure, and , in most instances, the fluid is identified with ultrasound to avoid injury to the liver, lung, or other tissues. The patient is positioned to make pleural fluid accessible to the examiner.

The patient's skin is prepared per protocol, the area is draped, and local anesthesia is injected subcutaneously. After allowing a short time for this to become effective, the thoracentesis needle is inserted above the rib to avoid damaging intercostal vessels, which run in a neurovascular bundle beneath each rib. The patient is advised not to move, cough, or take a deep breath during the procedure to reduce the risk of injury. When the needle contacts the fluid pocket, fluid can be withdrawn by gravity drainage or with suction. When indicated after removal of the thoracentesis needle or cannula, a larger bore thoracostomy tube may be inserted to provide additional drainage.

During thoracentesis, health care professionals should assess the patient for difficulty in breathing, dizziness, faintness, chest pain, nausea, pallor or cyanosis, weakness, sweating, cough, alterations in vital signs, oxygen saturation levels, or cardiac rhythm. An occlusive dressing should be applied to the puncture site as the needle or cannula is removed, preventing air entry. The fluid obtained is labeled and sent for diagnostic tests as ordered (typically Gram stain, cultures, cell count, measurements of fluid chemistries, pH, and , when appropriate, cytology). The amount, color, and character of the fluid is documented, along with the time of the procedure, the exact location of the puncture, and the patient's reaction. After the procedure, a chest x-ray is often obtained to assess results or determine if any injury has occurred, e.g., pneumothorax. The patient should be positioned comfortably. Vital signs are monitored until stable, then as needed. The patient is advised to call for assistance immediately, if difficulty in breathing or pleuritic pain is experienced.

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