Thoracocentesis - Procedure Description.

Thoracocentesis or pleural tap, is an invasive procedure to remove fluid or air from the pleural space for diagnostic or therapeutic purposes.
Drainage of the pleural space can be performed at the bedside.

Indications for this procedure include

• diagnostic evaluation of pleural fluid, 
• removal of pleural fluid for symptomatic relief, and 
• instillation of sclerosing agents in patients with recurrent, usually malignant pleural effusions.

Preparation: 

• Familiarity with the components of a thoracentesis tray is a prerequisite to performing a thoracentesis successfully. 
• Recent posterior-anterior (PA) and lateral chest radiographs with bilateral decubitus views should be obtained to document the free flowing nature of the pleural effusion. 
• Loculated pleural effusions should be localized by ultrasound or CT prior to drainage. 
• Management should be individualized in patients with a coagulopathy of thrombocytopenia. Thoracentesis is more challenging in patients with mechanical ventilation and should be performed with ultrasound guidance if possible.

Technique: 

• A posterior approach is the preferred means of accessing pleural fluid. 
• Comfortable positioning is a key to success for both patient and physician. 
• The patient should sit on the edge of the bed, leaning forward with the arms abducted onto a pillow on a bedside stand.
• Patients undergoing thoracentesis frequently have severe dyspnea, and it is important to assess if they can maintain this positioning for at least 10 min. 
• The entry site for the thoracentesis is based on the physical examination and radiographic findings. Percussion of dullness is utilized to ascertain the extent of the pleural effusion with the site of entry being the first or second highest interspace in this area. 
• The entry site for the thoracentesis is at the superior aspect of the rib, thus avoiding the intercostal nerve, artery, and vein, which run along the inferior aspect of the rib.
• The site of entry should be marked with a pen to guide the thoracentesis. 
• The skin is then prepared and draped in a sterile fashion with the operator observing sterile technique at all times. 
• A small-gauge needle is used to anesthetize the skin, and a larger-gauge needle is used to anesthetize down to the superior aspect of the rib. The needle should then be directed over the upper margin of the rib to anesthetize down to the parietal pleura. The pleural space should be entered with the anesthetizing needle, all the while using liberal amounts of lidocaine.
• A dedicated thoracentesis needle with an attached syringe should next be utilized to penetrate the skin. This needle should be advanced to the superior aspect of the rib. While maintaining gentle negative pressure, the needle should be slowly advanced into the pleural space. 
• If a diagnostic tap is being performed, aspiration of only 30–50 mL of fluid is necessary before termination of the procedure. 
• If a therapeutic thoracentesis is being performed, a three-way stopcock is utilized to direct the
• aspirated pleural fluid into collection bottles or bags. No more than 1 L of pleural fluid should be withdrawn at any given time, because quantities >1–1.5 L can result in re-expansion pulmonary edema.
• After all specimens have been collected, the thoracentesis needle should be withdrawn and the needle site occluded for at least 1 min.

Specimen Evaluation: The diagnostic evaluation of pleural fluid depends on the clinical situation. All pleural fluid samples should be sent for cell count and differential, Gram stain, and bacterial cultures. LDH and protein determinations should also be made to differentiate between exudative and transudative pleural effusions. The pH should be determined if empyema is a diagnostic consideration. Other studies on pleural fluid include mycobacterial and fungal cultures, glucose, triglyceride level, amylase, and cytologic determination.

Post procedure: A postprocedural chest radiograph should be obtained to evaluate for a pneumothorax, and the pt should be instructed to notify the physician if new shortness of breath develops.