Thoracentesis is a procedure commonly performed to evaluate or treat fluid collections in the pleural space. Diagnostic thoracentesis is indicated for most newly discovered pleural fluid collection of unknown origin. Approximately 1.5 million individuals in the United States develop a pleural effusion annually, and the cause can be determined in 75% of these cases by performing appropriate cytologic, hematologic, microbiologic, and chemical analyses of the fluid.
Approximately 10 to 20 mL of fluid is normally present in the pleural space. This low-protein fluid acts as a lubricant during respiration. The pleural pressure gradient between the systemic circulation to the parietal surface (chest wall) and the pulmonary circulation to the visceral surface (lung) produces a daily flow of about 10 mL of fluid through the pleural space. Many disease states can produce disruption of hydrostatic pressure, osmotic pressure, capillary permeability, or lymphatic drainage, with the resulting formation of abnormal collections of fluid in the pleural space. Estimates of the volume of pleural fluid can be made from the chest x-ray film. Blunting of the costophrenic angle correlates with 100 to 150 mL of fluid, opacification of one half of a hemithorax is produced by 1.0 to 1.5 L of fluid, and complete opacification of a hemithorax is produced by 2.5 to 3.0 L of fluid.
Several laboratory tests help to characterize abnormal pleural fluid collections as transudates or exudates (Table 3-1). Transudates, with a limited number of diagnostic possibilities, are generally associated with imbalances of hydrostatic and oncotic pressures. Transudates are noninflammatory effusions that generally have low numbers of lymphocytes and a predominance of monocytes. Exudates
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result from a legion of diagnostic possibilities and are caused by pleural inflammation and impaired lymphatic drainage of the pleural space. In acute stages, exudates have high leukocyte counts and a predominance of lymphocytes. The distinction between a transudate and exudate directs the clinician to the appropriate differential diagnoses and subsequent treatment options (Tables 3-2 and 3-3). Exceptions exist in the classification of effusions, because 20% of effusions associated with pulmonary embolus and 6% associated with malignancy are transudates. Observation of the pleural fluid also can provide clues to its cause (Tables 3-4 and 3-5).
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TABLE 3-1. CHARACTERISTICS OF PLEURAL EXUDATES |
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TABLE 3-2. CAUSES AND PROPERTIES OF TRANSUDATIVE PLEURAL EFFUSIONS |
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TABLE 3-3. CAUSES AND PROPERTIES OF EXUDATIVE PLEURAL EFFUSIONS |
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TABLE 3-4. DIAGNOSIS SUGGESTED BY EXAMINATION OF PLEURAL FLUID |
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TABLE 3-5. STUDIES PERFORMED IN COMPLETE PLEURAL FLUID ANALYSIS |
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Medications can produce pleural fluid collections. A number of medications (e.g., procainamide, hydralazine, isoniazid, phenytoin, quinidine) produce drug-induced lupus syndrome and pleural fluid collections that are indistinguishable from those of native lupus erythematosus. Medications that can directly produce effusions include nitrofurantoin, dantrolene, methysergide, methotrexate, bromocriptine, minoxidil, and amiodarone.
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Thoracentesis is considered relatively safe. The most common complication after thoracentesis is pneumothorax, with an average incidence of 6% to 19%. Uncontrollable coughing during the procedure and the use of large-bore needle without catheters may increase the likelihood of pneumothorax. Reexpansion pulmonary edema can be seen when large effusions are removed or when fluid removal allows atelectatic lung tissue to re-expand, especially if the lung has been collapsed for more than 7 days. Hemorrhage develops in less than 2% of procedures and necessitates thoracic surgery consultation if the bleeding is not controlled in 30 to 60 minutes.
Chest radiographs have been routinely performed after thoracentesis. Several studies question the practice and suggest that routine performance of the study in an asymptomatic individual after an uncomplicated procedure adds no management benefit. If multiple needle passes are required before fluid is obtained, if the patient has a history of chest irradiation or a prior sclerosing technique, or if an air leak is detected during the procedure, obtaining chest radiograph is indicated.
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INDICATIONS
RELATIVE CONTRAINDICATIONS
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PROCEDURE
The patient is seated, with the arms crossed and the body resting comfortably on a support (e.g., sturdy adjustable table) placed horizontally in front of the body. A footstool can be used to flex the patient's upper legs. The thorax should be erect. Alternately, for patients who cannot tolerate a seated position, the left lateral decubitus position can be used.
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(1) Seat the patient with the arms crossed and body resting comfortably on a support placed horizontally in front of the body. |
PITFALL: Complications can develop if the table supporting the patient suddenly shifts during the procedure. Make sure the table will not shift and that it can support the weight of the patient's torso during the procedure.
PITFALL: Avoid having the patient lean too far forward. Gravitational forces may cause the fluid to shift more anteriorly, increasing the likelihood of a postprocedure pneumothorax.
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Determine the level of effusion by percussion (Figure 2A). The level is determined by the point where the resonant percussion tone of the lungs changes to a dull percussion tone of the fluid. The needle insertion site should be one intercostal space below the level of effusion, at the upper portion of the rib and midway between the posterior axillary line and the paraspinal muscles (Figure 2B). An alternate approach is to insert the needle above the eighth rib, as low in the effusion as possible. Mark the site by indenting the skin firmly with a fingernail or pen cap.
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(2) After you have determined the level of effusion by percussion, mark the needle insertion site, which is located one intercostal space below the level of the effusion, at the upper portion of the rib, and midway between the posterior axillary line and the paraspinal muscles, by indenting the skin firmly with a fingernail or pen cap. |
PITFALL: Have the preprocedure chest radiograph immediately available for review. Aspiration of the wrong hemithorax is an embarrassing and dangerous error.
PITFALL: Most experts recommend a lateral decubitus x-ray film to make sure the fluid layers. Loculated fluid collections can be difficult to tap and are best approached with imaging guidance (i.e., ultrasound or computed tomography scan). Obtain the decubitus films before performing thoracentesis.
PITFALL: Routine approaches that are performed lower in an effusion (to hit the main fluid collection) may have greater risk of liver or splenic perforation.
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Apply sterile gloves, and have an assistant open the sterile thoracentesis tray. Swab a large area around the insertion site with povidone-iodine. Alternately, some physicians apply antiseptic solution before application of sterile gloves. Center the fenestration on the drape over the insertion site. Avoid contamination of the sterile gloves during this step.
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(3) Once gloved, swab a large area around the insertion site with povidone-iodine, and center the fenestration of the drape over the site. |
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Draw up the lidocaine into the 5-mL syringe. Use the small (25-gauge, 5/8-inch) needle to create a skin wheal (about 1 cm3) at the insertion site. The large (22-gauge, 1½-inch) needle is then placed on the syringe, and the needle tip is inserted to the upper portion of the rib. A small amount (about 1 mL) of anesthetic is administered, and the needle tip is backed up and redirected above the rib until the pleural surface is reached. Some authors advocate administering lidocaine after passing the upper rib every 2 mm of insertion of the needle tip. Fluid may be aspirated on reaching the pleura. After fluid is detected, back up the needle slightly, and administer the remaining anesthetic. Note the depth of insertion of the needle to reach the pleura. Remove the anesthesia needle, and place it back on the tray.
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(4) Create a skin wheal (about 1 cm3) at the insertion site by using a small-gauge needle, and then with a large-gauge needle attached to a 5-mL syringe containing lidocaine, insert the tip into upper portion of rib, administer a small amount (about 1 mL) of anesthetic, and continue to redirect above rib until pleural space is reached. |
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The thoracentesis needle is attached to the large (60-mL) syringe and inserted through anesthetized skin until the rib is reached. The needle is then redirected above the rib into the pleural space (Figure 5A). The path of the needle is a Z insertion track (Figure 5B). On removal of a needle through a Z track, the natural position of the tissues tends to reduce the chances for leaking fluid.
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(5) Insert the thoracentesis needle through anesthetized skin into the pleural space using the Z insertion track technique. |
PITFALL: Extensive bleeding can result from damage to an intercostal artery from the large thoracentesis needle. Always insert the needle just at the upper edge of the rib to avoid the neurovascular bundle that lies beneath each rib.
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Although many physicians perform thoracentesis using a straight needle, others prefer to withdraw fluid with a blunt (Tuohy) needle or flexible catheter because of concern about injury to the lung as the fluid is withdrawn. The following text describes the use of a catheter system. On reaching the pleural fluid, advance the soft plastic catheter through the needle. The needle can be withdrawn from the chest cavity while the catheter is held firmly stationary (i.e., needle withdrawn while the catheter remains in the pleural cavity.) The hard plastic catheter guard can be fastened over the needle tip to prevent damage to the catheter from the sharp bevel. The syringe can be reattached and pleural fluid aspirated. Do not permit air to enter the pleural space during this portion of the procedure. Usually, 35 to 50 mL is adequate for the pleural fluid studies. If a therapeutic procedure is performed, the stopcock can be attached to the drainage tubing and bag and a larger volume of fluid collected.
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(6) After the pleural fluid has been reached, advance the soft plastic catheter through the needle, and aspirate the pleural fluid. |
PITFALL: Do not attempt to withdraw the catheter through the needle, because the plastic catheter can be severed and fall into the pleural space.
PITFALL: Make sure an adequate length of catheter is inserted into the pleural space before the needle is withdrawn. It is frustrating if the catheter inadvertently comes out of the pleural space when the needle is withdrawn and before fluid has been obtained.
PITFALL: Do not attempt the removal of more than 1.5 L of fluid in a single setting. Reexpansion pulmonary edema can result, exacerbating the temporary (and usually minor) hypoxemia that follows thoracentesis. Oxygen should be administered if dyspnea occurs after the procedure. Close clinical monitoring is advocated whenever an individual has more than 1 L of fluid removed.
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The catheter is removed at the end of the procedure (or needle and catheter simultaneously). The insertion site is gently rubbed, and pressure is applied with gauze to the site to ensure the absence of a fluid leak. The skin site is washed clean, and a bandage is applied to the site.
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(7) Remove catheter or needle, or both, and rub and apply pressure to the site, making sure no fluid is leaking. Conclude by washing and dressing the site. |
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CODING INFORMATION
If imaging is used to guide the needle placement, alternate codes are selected (76003, 76360, or 76942). Code 32002 is used for thoracentesis with insertion of a tube (with or without a water seal) for drainage of a pneumothorax; code 32002 is not used to report chest tube placement for drainage of the pleura of blood or pus (32020).
Medicare allows for the separate billing of a thoracentesis tray (Healthcare Common Procedure Coding System [HCPCS] code A4550), and other insurance companies may also permit separate billing for a tray (99070) in addition to 32000 when the procedure is performed in office.
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INSTRUMENT AND MATERIALS ORDERING
Thoracentesis trays that include all instruments needed to perform the procedure can be ordered from Allegiance Healthcare Corp., McGraw Park, IL 60085 (phone: 847-689-8410; http://www.cardinal.com/allegiance) and from AVID Medical, Inc., Toano, VA 23168 (phone: 888-564-7153; http://www.avidmedical.com). Complete trays often include the following items:
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