Thoracentesis: What is it? Benefits, Procedure and Contraindications

It is a medical practice used for the diagnosis and treatment of pleural conditions.

In particular, thoracentesis is reserved for pathologies such as hypertensive pneumothorax and pleural effusion, in which there is, respectively, the accumulation of air and fluid within the pleural cavity and sometimes, to carry out pleurodesis.

Thoracentesis is an invasive procedure, performed under local anesthesia: the specialist, after inserting a needle or cannula directly into the patient’s chest, inhales excess fluid or air.

Chest x-rays are usually done after a thoracentesis is performed to rule out the presence of a pneumothorax.


This practice allows to quantify the magnitude of the fluid that has been extracted, as well as to visualize the lung fields that were previously difficult to observe because of the fluid present in the lungs.

There is evidence to suggest that chest radiographs are not necessary in asymptomatic patients.

The appearance of the cough is profuse as the lungs re-expand and this does not necessarily mean the appearance of a pneumothorax.

When there is inflammation in the pleural process, there may be pain and an audible pleural sound when the fluid is being eliminated, due to the proximity of the inflamed pleurae (visceral and parietal).

When large volumes of fluid are withdrawn from this pleural space, fluid should be released periodically from the syringe plunger during aspiration.

Since if the liquid in the syringe returns to the pleural space when the negative pressure has been decreased, it can be excessively negative and lung re-expansion be restricted due to adhesions or another factor in the lung.


The thoracentesis procedure can be safely performed in an outpatient setting.

Through chest percussion and imaging techniques, the presence and location of pleural fluid can be verified.

In cases where chest radiographs are questionable or if previous thoracentesis attempts were unsuccessful or the fluid is septum, ultrasound or computed tomography may be helpful.

During thoracentesis, the use of ultrasound increases success rates and decreases complications.

It is recommended to inform the doctor if the patient is allergic to certain medications, such as lidocaine, non-steroidal anti-inflammatory drugs among others.

As well as medications that can alter blood clotting, such as Coumadin, Sintrom and aspirin.

Thoracentesis is easier to perform and is also safer if the patient is sitting slightly leaning forward or in an upright position.

Thoracentesis can also be performed with the patient in a supine position as in the case of a ventilated patient, when performed supported by an ultrasound or a computed tomography scan.

This procedure only requires monitoring such as pulse oximetry and an electrocardiogram in those cases of patients who present high risks of decompensation or in unstable patients.

Lidocaine at a concentration of 1 to 2% is injected with a 25-gauge needle to numb the skin.

Taking great care to perform it under sterile conditions.

Then it is introduced, at the upper edge of the rib, this is an intercostal space located below the liquid level of the mid scapular line.

The gauge of this needle ranges from 20 or 22 accompanied by anesthesia, A periodic aspiration is performed, to avoid that it is involuntarily inserted into a blood vessel, intravascular injection and anesthesia are introduced at deeper levels.

The maximum infiltration should be received by the parietal pleura, which is the most painful level after the skin.

The needle is then inserted beyond the parietal pleura until reaching the pleural fluid, at this time, the depth to which the needle was inserted should be inspected.

Next, a 16 to 19 gauge thoracentesis needle catheter is inserted into a 3-way stopcock, this in turn is connected to a 30 to 50 milliliter syringe and the tubing will drain into a reservoir.

The catheter is then inserted through the needle and to decrease the risk of pneumothorax, the needle is removed.

Now the pleural fluid is aspirated with a turn of the 3-way stopcock, and collected in tubes or bags for further evaluation.

Usually the fluid that is eliminated is done in stages that do not exceed a volume of 1.5 liters per day, since there is a risk that hypotension and pulmonary edema may occur if more than 1.5 liters of fluid are extracted. at once.

But there is little evidence that reexpansion pulmonary edema is related to the volume of pleural fluid removed, so highly experienced professionals drain effusions in a single procedure.

When large volumes of fluid are drained, blood pressure should be monitored continuously and thoracentesis should be discontinued if the patient has chest pain or when pleural pressure drops below 20 cm H2O.


Contraindications to performing a thoracentesis are:

  • Congestive heart failure with bilateral effusion.
  • Coagulation disorders.
  • Pulmonary emphysema
  • Severe cardiopulmonary failure.
  • Established pleural adherence.
  • Chest wall infections at the injection site.
  • Rupture of the diaphragm.

The relative contraindications are:

  • Uncertain location of fluid on examination.
  • When the volume of fluid in the lungs is minimal.
  • The chest wall is altered in its anatomy.
  • Serious lung diseases that could lead to life-threatening complications.
  • Hemorrhagic diathesis or coagulopathy.
  • Uncontrollable cough


The complications are:

  • That a pneumothorax occurs.
  • That the pulmonary puncture causes a hemoptysis.
  • Pulmonary edema due to re-expansion or hypotension (rare, and probably not related to the volume of fluid withdrawn).
  • Damage to the intercostal vessels that can cause a hemothorax.
  • Puncture in the spleen or liver.
  • Neurocardiogenic Syncope.

In some particularly severe clinical situations, such as hemothorax, hypertensive pneumothorax, and large pleural effusion, the patient is at risk of severe cardiopulmonary disturbance.

In such circumstances, when the accumulation of air or fluid has a strong impact on the function of the heart and lungs, it is advisable to undergo a thoracotomy (open drainage of the pleural cavity).