It is an essential procedure for critical care physicians and emergency physicians.
With proper training in both thoracentesis and the use of ultrasound , clinicians can safely and successfully perform this procedure.
Before the procedure, bedside ultrasound can be used to determine the presence and size of pleural effusions and to look for loculations .
During the procedure, anesthesia can be used to facilitate the process and then guide the placement of the needle.
Thoracentesis is indicated for the symptomatic treatment of large pleural effusions or for the treatment of empyemas.
It is also indicated for pleural effusions of any size that require diagnostic analysis.
Some fluid is usually found in the pleural space. However, too much fluid enters the layers of the pleura creates a pleural effusion.
So this test is done to find out what is causing the extra fluid or to relieve symptoms from fluid build-up.
Analysis of the fluid will help the doctor determine the cause of the pleural effusion. Possible causes can be:
- Liver failure.
- Heart failure.
- Low protein levels.
- Renal disease.
- Asbestos-related pleural effusion.
- Collagen vascular disease (a class of disease in which the body’s immune system attacks its own tissue).
- Drug reactions.
- Collection of blood in the pleural space (hemothorax).
- Lung cancer.
- Inflammation and swelling of the pancreas (pancreatitis).
- Blockage of an artery in the lungs (pulmonary embolism).
- Severe hypothyroidism.
There are no absolute contraindications to thoracentesis. Relative contraindications include the following:
- Uncorrected bleeding diathesis.
- Chest wall of cellulite at the puncture site.
A 2017 review of the literature on post-procedural, intraoperative, and post-procedural aspects of thoracentesis suggested the following:
It is necessary that the specialist receives training from the doctor and maintenance of skills, such as a simulation with direct observation.
In turn, it is necessary for the doctor to be familiar with moderate coagulopathy, that is:
- The international normalized index must be at a score less than 3.
- The platelet count must be greater than 25,000 / μl.
It is important to mention that mechanical ventilation does not increase the risk of post-procedure complications.
At the time of the procedure
During the procedure, it is important to know that ultrasonography is associated with a lower risk of pneumothorax.
In addition, pleural manometry can help identify the non-expansive lung and can reduce the risk of re-expansion of pulmonary edema.
Finally, routine chest radiography is not justified because bedside ultrasound can identify pneumothorax.
Complication rates for thoracentesis performed by experienced physicians depend on the condition of the patient, although they generally do not arise.
However, the data on complications that develop after thoracentesis performed by residents learning the procedure are significant.
The main complications include the following:
- Pneumothorax (11% probability).
- Hemothorax (0.8% probability).
- Laceration of the liver or spleen (0.8% probability).
- Diaphragmatic injury.
- Tumor seeding.
Minor complications include the following:
- Pain (22% probability).
- Cough (11% probability).
- Subcutaneous hematoma (2% probability).
- Subcutaneous seroma (0.8% probability).
- Síncope vasovagal.
- Analgesia and sedation.
General analgesia and local anesthesia are mandatory, except with tension pneumothorax, as it is immediately fatal.
The experienced physician should consider sedating the patient during the procedure depending on the condition of the procedure.
Nitrous oxide should not be used as it can enter the pleural space by diffusion and rapidly increase the volume of the pneumothorax.
Similarly, the physician should consider oral or parenteral analgesia before and after the procedure.
It is important to mention that the placement and presence of an intercostal catheter device is painful and can cause discomfort previously.
It is very important that the physician places the patient on continuous cardiac monitoring and pulse oximetry during the process.
The traumatized person should be placed in the supine position. All other patients should be in a 45 degree sitting position.
Both positions are shown in depth below:
Performing the procedure in this position is more comfortable in a seated position for both the patient and the physician.
The patient should lean forward slightly and support the head on the arms or hands or on a pillow placed on an adjustable nightstand.
This position facilitates access to the posterior axillary space, which is the most dependent part of the thorax.
Unstable patients and those who cannot sit up can be approached supine for the procedure.
The patient is moved to the end of the bed, the ipsilateral hand is placed behind the head, and a towel roll is placed under the contralateral shoulder. This measure facilitates dependent drainage.
The injection applies the largest pocket of superficial fluid to the lung.
Traditionally, this is found between the seventh and ninth rib spaces and between the posterior axillary line and the midline.
However, alternatively, it can be placed in the fourth or fifth intercostal space, located just anterior to the mid-axillary line.
Bedside ultrasound can confirm the optimal puncture site, which is then marked.
Ultrasound can increase the chance of obtaining pleural fluid and reduce the complications of the procedure.
To place the injection, the doctor must palpate the landmark (the second intercostal space, on the upper edge of the rib in the midclavicular line) and antiseptically prepare the area.
After the site is disinfected with chlorhexidine solution (currently preferred over povidone or iodine) and sterile drapes are placed.
Local anesthesia must be infiltrated, slowly advancing to the pleural fluid. A needle with a larger hole can be used if necessary.
The correct location for thoracentesis should be confirmed by aspirating pleural fluid before inserting needles or larger thoracentesis catheters.
Next, the doctor should place a 5 ml syringe in the catheter device (cannula or pigtail).
The cannula should be inserted vertically into the chest wall, just above the lower rib. It is important that during this stage the patient breathes in at all times.
In tension pneumothorax, you will often hear a pop or feel a change in resistance.
The needle should then be withdrawn while gently advancing the cannula down into position.
The cannula should be secured with tape. It is necessary to fit a 3-way tap and a 20 ml / 50 ml syringe.
Through the route it should be drained until there is no more drainage at a maximum of 30 ml / kg (maximum 2.5 L).
After this, it is very important not to remove the suction device until a decision is made that the patient will not need additional drainage.
Device or catheter insertion and effusion drainage
Initially, the skin must be cut with a number 11 scalpel blade by the specialist.
The thoracentesis device is inserted over the upper side of the rib until pleural fluid is obtained.
It is very important to mention that the neurovascular bundle is located on the lower edge of the rib and should be avoided in all circumstances.
Most commercial devices have a marker at 5 cm indicating that the entrance to the hemithorax is generally entered and the needle does not need to advance further.
This 5 cm mark should be skin level to avoid further complications.
The catheter is fed over the needle introducer and this happens all the way to the center.
The pleural effusion is drained with a syringe pump or vacuum bottle, until the desired volume has been removed for symptomatic relief or diagnostic analysis.
Finally, the catheter or needle is carefully removed, and the wound is covered.
A minimum of 20 ml would be sufficient for basic analysis. Most diagnostic procedures remove less than 100 ml of fluid.
For therapeutic purposes, only moderate amounts of pleural fluid should be removed to prevent re-expansion of pulmonary edema and to avoid causing a pneumothorax.
Removal of 400-500 ml of pleural fluid is often sufficient for shortness of breath. The maximum recommended limit is 1000-1500 ml in a single thoracentesis procedure.
Pleural pressure should be monitored with a manometer, this is very useful, since the appearance of pressure or pain in the chest during the extraction of fluid indicates a lung that does not expand freely.
If this happens the procedure should be stopped immediately to avoid re-expansion of the pulmonary edema (pulmonary edema in the context of rapid expansion of a collapsed lung).
Pain occurs frequently during fluid removal, and this is not an indication to stop the procedure, unless the cough it generates causes discomfort to the patient.
The physician should reevaluate the patient’s condition and take into account the following:
- Consider the need for increased analgesia.
- Organize the appropriate disposition of the patient.