Thoracentesis
Thoracentesis is indicated for diagnostic or therapeutic drainage of pleural fluid. A diagnostic thoracentesis can be performed with little more than a spinal needle and a 10 cc syringe, while large volume thoracentesis warrants intrathoracic catheter placement. There are no absolute contraindications to thoracentesis. Patients with thrombocytopenia (< 50k) or other bleeding risk should be discussed with hematology to determine if pretreatment with FFP (platelets not available at this facility) is indicated. Failure to drain a significant amount of fluid is typically the result of loculations; a lateral decubitus CXR may assist in determining if fluid is freely moving or loculated.
The greatest risk of thoracentesis is pneumothorax. As dullness to percussion of fluid is unreliable, all thoracentesis benefits from ultrasound guidance. While it is not necessary to perform the entirety of the procedure under ultrasound, marking the deepest fluid cavity with ultrasound allows for the safest approach. At YKHC our kits include a Safe-T-Centesis needle, further decreasing the risk on pneumothorax. Other complications include infection, bleeding and damage to intraabdominal organs.
Technique
- Position patient in seated position, leaning forward with arms and head supported, similar to positioning for lumbar puncture.
- Using ultrasound with phased array (cardiac) probe, determine where the deepest fluid pocket is that is safely inferior to the lingula of the lung and safely superior to the diaphragm.
- Prep skin with chlorhexidine or povidone-iodine and sterilely drape patient.
- Inject small amount of lidocaine at point of entry and over the superior aspect of the rib, avoiding the intercostal vessels which run on the inferior aspect of ribs. Inject and aspirate until at the level of the pleura.
- Attach a 3 way stopcock and syringe to the thoracentesis needle.
- Insert the thoracentesis needle slowly while pulling back on the syringe. Traditionally the thoracentesis needle is inserted using Z-track method to help prevent persistent pleural fluid leakage.
- Once pleural fluid is obtained, keep the needle in place and push the catheter over the needle and into the thoracic cavity.
- Drain as much fluid as necessary, then remove drain and cover with occlusive (petroleum gauze) dressing.
- Send fluid for appropriate testing, and there is an ‘ED Thoracentesis’ order set to assist with this.
Traditionally it was recommended to not remove > 1500 mL to avoid reexpansion pulmonary edema (RPE) from low pleural pressures rapidly shifting fluid into the lungs. There is actually no evidence that removing large volumes causes more risk of RPE harm than removing small volumes, thus it is recommended to drain as much fluid as possible as the risk of iatrogenic harm from repeated procedures outweighs the risk of RPE. When RPE occurs it is typically more dramatic radiographically than clinically, as it is usually well tolerated and treated with supportive care.
Resources/References
- Farkas, J. Large volume thoracentesis: How much can safely be removed?. PulmCrit (2014).
- UCSD Standardized Procedure Thoracentesis (Adult)
- Thomsen et al. Thoracentesis. N Engl J Med 2006; 355:e16. DOI: 10.1056/NEJMvcm053812 (video)
