Patient information: Thoracentesis

THORACENTESIS OVERVIEW

Thoracentesis is a procedure used to obtain a sample of fluid from the space around the lungs. Normally, only a thin layer of fluid is present in the area between the lungs and chest wall (picture 1). However, some conditions can cause a large amount of fluid to accumulate. This collection of fluid is called a pleural effusion (picture 2). Thoracentesis is done to collect a sample of the fluid, which can help determine why the pleural effusion developed.

REASONS FOR THORACENTESIS

A thoracentesis is performed to determine the cause of a pleural effusion. In some cases, a physician may perform thoracentesis to relieve symptoms caused by the pleural effusion, including shortness of breath and low blood oxygen levels. A pleural effusion may be detected during a physical examination or on a chest x-ray.

Pleural effusion can be caused by many different conditions, including infections, heart failure, cancer, or tuberculosis. In some cases, blood or other fluid may be leaking into the pleural space from another part of the body, causing the effusion. By examining the fluid and the types of cells it contains, the cause of the effusion can usually be determined.

In general, there is no reason a thoracentesis cannot be performed. The procedure is more easily performed and complications are less common when the pleural effusion is large.

If you have a bleeding disorder or are on medications that affect blood clotting, you may need extra care to minimize the risk of bleeding. Tell your healthcare provider if you have a history of bleeding problem or if you are taking medicine that decreases blood clotting. In some cases, a blood test will be taken prior to the procedure to exclude any blood clotting abnormalities caused by disease or medications.

THORACENTESIS PREPARATION

Before a thoracentesis, a chest x-ray will be taken to identify the location of the pleural effusion. The doctor will explain the procedure and discuss why it is necessary. He or she will examine the chest closely; the edge of the effusion can often be identified by listening to the lungs and tapping on the chest wall.

Ultrasound machines are used routinely in many institutions to increase the safety of the procedure. Ultrasound guidance is recommended when the fluid is trapped in small pockets around the lung.

The procedure takes a short time and can be performed at a patient's bedside or in a physician's office.

THORACENTESIS PROCEDURE

A thoracentesis involves the following steps:

• You will be placed in a position that allows the doctor to easily access the effusion. Usually, you are asked to sit upright during the procedure. It is important to remain still during the procedure so that the fluid does not shift.
• A small amount of numbing medicine (a local anesthetic, similar to novocaine) is injected into the area. This medicine helps minimize discomfort during the procedure.
• A slightly larger needle is inserted in the same location. A syringe is attached to this needle and is used to withdraw fluid from around the lung. If you have symptoms from the effusion (eg, shortness of breath),a large amount of fluid may be removed, which allows the lung to re-expand.

THORACENTESIS COMPLICATIONS

In most cases, a thoracentesis is performed without complications. Most complications are minor and resolve on their own or are easily treated. Potential complications include the following:

• Pain — Some discomfort may occur when the needle is inserted. Using a local anesthetic helps to reduce the pain. Pain generally resolves once the needle is removed.
• Bleeding — A blood vessel may be nicked as the needle is inserted through the skin and chest wall, causing bleeding. The bleeding is usually minor and stops on its own, although it may cause bruising around the puncture site. In rare cases, bleeding into or around the lung may occur, requiring drainage or surgery.
• Infection — Infection can occur if bacteria are introduced by the needle puncture. Using disinfectant solution to clean the area and using sterile technique during the procedure minimizes this risk.
• Pneumothorax or collapsed lung — Occasionally, the needle used to obtain a fluid sample can puncture the lung. The hole created by the puncture usually seals quickly on its own. If it does not, air can build up around the lung, causing the lung to collapse. This is called a pneumothorax. When a pneumothorax occurs, a chest tube may be used to drain the air and allow the lung to re-expand.

A pneumothorax may also occur if the lung fails to expand when fluid is withdrawn. This is considered to be a drainage-related pneumothorax, and is the most common type of pneumothorax to occur when ultrasound is used for needle placement. Drainage-related pneumothorax is most commonly caused by disorders of the surface lining of the lung and not by the puncture needle. Treatment is rarely needed.

Pneumothorax occurs in less than 12 percent of procedures. Those that do occur are usually small and resolve on their own. A chest tube to helps re-expand the lung is necessary only if the pneumothorax is large, continues to expand, or causes symptoms.

• Liver or spleen puncture — In very rare cases, the liver or spleen may be punctured during thoracentesis. Sitting upright and remaining still during the procedure helps to keep the liver and spleen away from the insertion area and minimizes the risk of this complication.

FOLLOWING THE THORACENTESIS PROCEDURE

After the procedure, the doctor will observe the insertion site for signs of bleeding and assess breathing for signs of lung collapse (pneumothorax). If a pneumothorax is suspected, a chest x-ray will be obtained. The doctor will examine the fluid, particularly its color and consistency, and will also send the fluid for laboratory tests.

In general, sedating medicines are not used during thoracentesis. If sedating medicines are used, the patient will need assistance getting home. Patients should discuss these issues with their physician prior to the procedure.

WHERE TO GET MORE INFORMATION

Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two people are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.

This discussion will be updated as needed every four months on our web site (www.uptodate.com/patients). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

Some of the most pertinent include:

Patient Level Information:

Professional Level Information:
An overview of medical thoracoscopy
Diagnostic evaluation of a pleural effusion in adults
Diagnostic thoracentesis
Imaging of pleural effusions in adults
Management of malignant pleural effusions

A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.

• American Thoracic Society

      (www.thoracic.org)

• American Lung Association

      (lungusa.org)

• National Heart Lung & Blood Institute

      (www.nhlbi.nih.gov/index.htm)

• National Library of Medicine

      (www.nlm.nih.gov/medlineplus/healthtopics.html)

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