The thorax is an enclosed space that houses the trachea and lungs, heart, and part of the esophagus along with other tissues. The space is bounded mostly by the rib cage and pulmonary diaphragm. In diseases of the thorax such as lung cancer, congestive heart failure and asbestos exposure, it is common for fluid to accumulate within this enclosed space. This accumulation of fluid is referred to as a pleural effusion.
As fluid accumulates in the thorax (chest) it causes a number of symptoms. If the pleural effusion is large enough, it can become life threatening. Fluid usually begins by pressing on the soft tissue of the lungs which makes breathing very difficult. Since the lungs require a slight vacuum (negative pressure) between the lung and the chest wall to inhale air, fluid in this space disrupts this vacuum and leads to a collapsed lung. With large amounts of fluid in the thoracic cavity, heart function can become compromised since the pleural effusion presses directly against the chambers of the heart.
For small pleural effusions with few symptoms, treatment is conservative and is directed at the root cause of the effusion. As the initial disease is corrected, the pleural effusion will be absorbed by the body. However for large or complicated pleural effusions the treatment of choice is a procedure called thoracentesis.
A thoracentesis is the removal of fluid from the chest cavity; thora- indicates thorax or the chest and the suffix -centesis means “to draw off fluid.” A needle is advanced into the chest cavity and fluid is withdrawn. If the pleural effusion is a thin fluid (transudate), it will follow gravity. Therefore patients are seated upright so that the effusion works its way into the lower chest. This is done so that the needle can remove the maximum amount of fluid with the least risk of injury to the patient. If the pleural effusion contains copious amounts of protein (exudate) the fluid may “coagulate” or “organize” in the chest and form pockets. In this case, the majority of fluid will not follow gravity and positioning is done to reach the largest pocket(s).
The procedure is planned based on X-rays of the patient’s chest while seated, reclining and while the patient is on his side.The patient’s back is exposed and sterilized. A thin needle is used to numb the back with a local anesthetic. Once the surface is numb, a larger needle is used to numb deeper areas. While wearing sterile garments and gloves, the physician feels for landmarks on the back. Increasingly, many physicians are using bedside ultrasound devices to locate the ribs and to confirm the precise location of the pleural effusion. Once the optimal location for drainage has been identified, a small nick in the skin is made with a scalpel blade. Then a large diameter needle is advanced until it reaches the pleural space. In most cases fluid will be forced out because of high pressure inside the chest. A catheter may be inserted and the fluid drawn out under gentle vacuum. Ultrasound and follow up X-rays are indicated to ensure that the fluid has been removed and the lung is inflated.
Thoracentesis is often done in a hospital setting since symptoms of a severe pleural effusion usually require hospitalization. However a thoracentesis is a “bedside” procedure which means it does not require a surgical theater. Thus chronic lung disease patients may have outpatient thoracenteses on occasion.
References
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