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Thoracentesis

Thoracentesis

Definition

Also known as pleural fluid analysis, thoracentesis is a procedure that removes fluid or air from the chest through a needle or tube.

Purpose

The lungs are lined on the outside with two thin layers of tissue called pleura. The space between these two layers is called the pleural space. Normally, there is only a small amount of lubricating fluid in this space. Liquid and/or air accumulates in this space between the lungs and the ribs from many conditions. The liquid is called a pleural effusion ; the air is called a pneumothorax. Most pleural effusions are complications emanating from metastatic malignancy (movement of cancer cells from one part of the body to another). Most malignant pleural effusions are detected and controlled by thoracentesis. Thoracentesis is also performed as a diagnostic measure. In these cases, only small amounts of material need to be withdrawn.

Symptoms of a pleural effusion include breathing difficulty, chest pain, fever, weight loss, cough, and edema. Removal of air is often an emergency procedure to prevent suffocation from pressure on the lungs. Negative air pressure within the chest cavity allows normal respiration. The accumulation of air or fluid within the pleural space can eliminate these normal conditions and disrupt breathing and the movement of air within the chest cavity. Fluid removal is performed to reduce the pressure in the pleural space and to analyze the liquid. In addition, thoracentesis was traditionally used to remove blood from the chest cavity. This is rare now that the placement of a thoracostomy tube has proven to be a more effective and safer method.

Thoracentesis often provides immediate abatement of symptoms. However, fluid often begins to reaccumulate. A majority of patients will ultimately require additional therapy beyond a simple thoracentesis.

There are two types of liquid in the pleural space, one having more protein in it than the other. More watery liquids are called transudates; thicker fluids are called exudates. On the basis of this difference, the cause of the effusion can more easily be determined.

Transudates

Thin, watery fluid oozes into the chest either because back pressure from circulation squeezes it out or because the blood has lost some of its osmotic pressure.

  • Heart failure creates back pressure in the veins as blood must wait to be pumped through the heart.
  • A pulmonary embolism is a blood clot in the lung. It will create back pressure in the blood flow and also damage a part of the lung so that it leaks fluid.
  • Cirrhosis is a sick, scarred liver that both fails to make enough protein for the blood and also restricts the flow of blood through it.
  • Nephrosis is a collection of kidney disorders that change the osmotic pressure of blood and allow liquid to seep into body cavities.
  • Myxedema is a disease caused by too little thyroid hormone.

Exudates

Thicker, more viscous fluid is usually due to greater damage to tissues, allowing blood proteins as well as water to seep out.

  • Pneumonia, caused by viruses and by bacteria, damages lung tissue and can open the way for exudates to enter the pleural space.
  • Tuberculosis can infect the pleura as well as the lungs and cause them to leak liquid.
  • Cancers of many types settle in the lungs or the pleura and leak liquids from their surface.
  • Depending upon its size and the amount of damage it has done, a pulmonary embolism can also produce an exudate.
  • Several drugs can damage the lung linings as an unexpected side effect. None of these drugs is commonly used.
  • An esophagus perforated by cancer, trauma, or other conditions can spill liquids and even food into the chest. The irritation creates an exudate in the pleural space.
  • Pancreatic disease can cause massive fluid in the abdomen, which can then find its way into the chest.
  • Pericarditis is an inflammation of the sac that contains the heart. It can ooze fluid from both sidesinto the heart's space and into the chest.
  • Radiation to treat cancer or from accidents with radioactive materials can damage the pleura and lead to exudates.
  • A wide variety of autoimmune diseases attacks the pleura. Among these are rheumatoid arthritis and systemic lupus erythematosus (SLE).
  • Many other rare conditions can also lead to exudates.

Blood

Blood in the chest (hemothorax) is infrequently seen outside of two conditions:

  • major trauma can sever blood vessels in the chest, causing them to bleed into the pleural space
  • cancers can ooze blood as well as fluid, they do not usually bleed massively

Chyle

Occasionally, the liquid that comes out of the chest is neither transparent nor bloody, but milky. This is due to a tear of the large lymphatic channelthe thoracic duct carrying lymph fluid from the intestines to the heart. It is milky because it is transporting fats absorbed in the process of digestion. The major causes of chylothorax are:

  • injury from major trauma, such as an automobile accident
  • cancers eroding into the thoracic duct

Air

Air in the pleural space is called pneumothorax. Air can enter the pleural space either directly through a hole between the ribs or from a hole in the lungs. Holes in the lungs are sometimes spontaneous, sometimes traumatic, and sometimes the result of disease opening a communication to the air in the lung.

Precautions

Care must be taken not to puncture the lung when inserting the needle. Thoracentesis should never be performed by inserting the needle through an area with an infection. An alternative site needs to be found in these cases. Patients who are on anticoagulant drugs should be carefully considered for the procedure.

Description

The usual place to tap the chest is below the armpit (axilla). Under sterile conditions and local anesthesia, a needle, a through-the-needle-catheter, or an over-the-needle catheter may be used to perform the procedure. Overall, the catheter techniques may be safer. Fluid or air is withdrawn. Fluid is sent to the laboratory for analysis. If the air or fluid continue to accumulate, a tube is left in place and attached to a one-way system so that it can drain without sucking air into the chest.

Preparation

The location of the fluid is pinpointed through x ray or ultrasound. Ultrasound is a more accurate method when the effusion is small. A sedative may be administered in some cases but is generally not recommended. Oxygen should be given to the patient.

Aftercare

As long as the tube is in the chest, the patient must lie still. After it is removed, x rays will determine if the effusion or air is reaccumulating%though some researchers and clinicians believe chest x rays do not need to be performed after routine thoracentesis.

Risks

Reaccumulation of fluid or air is a possible complications, as are hypovolemic shock (shock caused by a lack of circulating blood) and infection. Patients are at increased risk for poor outcomes if they have a recent history of anticoagulant use, have very small effusions, have significant amounts of fluid, have poor health leading into this condition, have positive airway pressure, and have adhesions in the pleural space. A pneumothorax can sometimes be caused by the thoracentesis procedure. The use of ultrasound to guide the procedure can reduce the risk of pneumothorax.

Thoracentesis can also result in hemothorax, or bleeding within the thorax. In addition, such internal structures as the diaphragm, spleen, or liver, can be damaged by needle insertion. Repeat thoracenteses can increase the risk of developing hypoproteinemia (a decrease in the amount of protein in the blood).

Resources

BOOKS

Abeloff, Martin D., et al., editors. Clinical Oncology. New York: Churchill Livingstone, 2000.

Celli, R. Bartolome. "Diseases of the Diaphragm, Chest Wall, Pleura and Mediastinum." In Cecil Textbook of Medicine, edited by J. Claude Bennett. Philadelphia: W. B. Saunders, 2000.

PERIODICALS

Colt, Henri G. "Factors Contributing to Pneumothorax After Thoracentesis." Chest 117 (February 2000).

Petersen, W.G. "Limited Utility of Chest Radiograph After Thoracentesis." Chest 117 (April 2000): 1038-1042.

KEY TERMS

Axilla Armpit.

Catheter A tube that is moved through the body for removing or injecting fluids into body cavities.

Hypovolemic shock Shock caused by a lack of circulating blood.

Osmotic pressure The pressure in a liquid exerted by chemicals dissolved in it. It forces a balancing of water in proportion to the amount of dissolved chemicals in two compartments separated by a semi-permeable membrane.

Pleura Two thin layers lining the lungs on the outside.

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Thoracentesis

Thoracentesis

Definition

Also known as pleural fluid analysis, thoracentesis is a procedure that removes an abnormal accumulation of fluid or air from the chest through a needle or tube.

Purpose

Thoracentesis can be performed as a diagnostic or treatment procedure. For diagnosis, only a small amount of fluid is removed for analysis. For treatment, larger amounts of air or fluid are removed to relieve symptoms.

The lungs are lined on the outside with two thin layers of tissue called pleura. The space between these two layers is called the pleural space. Normally, there is only a small amount of lubricating fluid in this space. Liquid and/or air accumulates in this space between the lungs and the ribs from many conditions. The liquid is called a pleural effusion ; the air is called a pneumothorax. Most pleural effusions are complications emanating from metastatic malignancy, or the movement of cancer cells from one part of the body to another; these are known as malignant pleural effusions. Other causes include trauma, infection, congestive heart failure, liver disease, and renal disease. Most malignant pleural effusions are detected and controlled by thoracentesis.

Symptoms of a pleural effusion include shortness of breath, chest pain, fever , weight loss , cough, and edema. Removal of air is often an emergency procedure to prevent suffocation from pressure on the lungs. Negative air pressure within the chest cavity allows normal respiration. The accumulation of air or fluid within the pleural space can eliminate these normal conditions and disrupt breathing and the movement of air within the chest cavity. Fluid removal is performed to reduce the pressure in the pleural space and to analyze the liquid.

Thoracentesis often provides immediate abatement of symptoms. However, fluid often begins to re-accumulate. A majority of patients will ultimately require additional therapy beyond a simple thoracentesis procedure.

Precautions

Thoracentesis should never be performed by inserting the needle through an area with an infection. An alternative site needs to be found in these cases. Before undergoing this procedure, a patient must make their doctor aware of any allergies, bleeding problems or use of anticoagulants, pregnancy, or possibility of pregnancy.

Description

Prior to thoracentesis, the location of the fluid is pinpointed through x ray , computed tomography (CT) scan, or ultrasound. Ultrasound and CT are more accurate methods when the effusion is small or walled off in a pocket (loculated). A sedative may be administered in some cases but is generally not recommended. Oxygen may be given to the patient.

The usual place to tap the chest is below the armpit (axilla) or in the back. Under sterile conditions and local anesthesia, a needle, a through-the-needle-catheter, or an over-the-needle catheter may be used to perform the procedure. Overall, the catheter techniques may be safer. Once fluid is withdrawn, it is sent to the laboratory for analysis. If the air or fluid continue to accumulate, a tube is left in place and attached to a one-way system so that it can drain without sucking air into the chest.

Preparation

Patients should check with their doctor about continuing or discontinuing the use of any medications (including over-the-counter drugs and herbal remedies). Unless otherwise instructed, patients should not eat or drink milk or alcohol for at least four hours before the procedure, but may drink clear fluids like water, pulp-free fruit juice, or tea until one hour before. Patients should not smoke for at least 24 hours prior to thoracentesis. To avoid injury to the lung, patients should not cough, breathe deeply, or move during this procedure.

Aftercare

After the tube is removed, x rays will determine if the effusion or air is reaccumulating, though some researchers and clinicians believe chest x rays do not need to be performed after routine thoracentesis.

Risks

Reaccumulation of fluid or air are possible complications, as are hypovolemic shock (shock caused by a lack of circulating blood) and infection. Patients are at increased risk for poor outcomes if they have a recent history of anticoagulant use, have very small effusions, have significant amounts of fluid, have poor health leading into this condition, have positive airway pressure, or have adhesions in the pleural space. A pneumothorax can sometimes be caused by the thoracentesis procedure. The use of ultrasound to guide the procedure can reduce the risk of pneumothorax.

Thoracentesis can also result in hemothorax, or bleeding within the thorax. In addition, internal structures, such as the lung, diaphragm, spleen, or liver, can be damaged by needle insertion. Repeat thoracenteses can increase the risk of developing hypoproteinemia (a decrease in the amount of protein in the blood).

Resources

BOOKS

Abeloff, Martin D., et al., eds. Clinical Oncology. New York:Churchill Livingstone, 2000.

Celli, R. Bartolome. "Diseases of the Diaphragm, Chest Wall, Pleura and Mediastinum." In Cecil Textbook of Medicine. Bennett, J. Claude, ed. Philadelphia: W. B. Saunders, 2000.

Miller, Don R. "Pleural Effusion and Empyema Thoracis." In Conn's Current Therapy. Rakel, Robert E., et al., eds. Philadelphia: W.B. Saunders, 1998.

Ross, David S. "Thoracentesis." In Clinical Procedures in Medicine. Roberts, James R., et al., eds. Philadelphia: W.B. Saunders, 1998.

PERIODICALS

Colt, Henri G. "Factors Contributing to Pneumothorax After Thoracentesis." Chest 117 (February 2000).

Petersen, W.G. "Limited Utility of Chest Radiograph After Thoracentesis." Chest 117 (April 2000): 1038-42.

J. Ricker Polsdorfer, M.D.

Mark A. Mitchell, M.D.

KEY TERMS

Axilla

Armpit.

Catheter

A tube that is moved through the body for removing or injecting fluids into body cavities.

Hypovolemic shock

Shock caused by a lack of circulating blood.

Osmotic pressure

The pressure in a liquid exerted by chemicals dissolved in it. It forces a balancing of water in proportion to the amount of dissolved chemicals in two compartments separated by a semi-permeable membrane.

Pleura

Two thin layers lining the lungs on the outside.

QUESTIONS TO ASK THE DOCTOR

  • How will thoracentesis benefit me?
  • Will I have to have this procedure more than once?
  • How soon after this procedure can I resume my normal activities?
  • Will this procedure cure my problem?
  • Will I require hospitalization?

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thoracentesis

thoracentesis (thor-ă-sen-tee-sis) n. see pleurocentesis.

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Thoracentesis

Thoracentesis

Definition

Thoracentesis is a procedure by which pleural fluid is removed from the space between the lung and the chest wall. The space in which this fluid collects is called the pleural space. It is formed in between the serous membrane covering each lung, called the visceral pleura, and the serous membrane covering the chest wall, called the parietal pleura. Normally very little fluid is present in the pleural space, and it serves to lubricate the two pleural surfaces, so they can easily slip across each other during respiration.

Purpose

Abnormal quantities of pleural fluid may accumulate in various conditions. Removal of pleural fluid for analysis is commonly performed in order to determine the cause of fluid accumulation. Sometimes the effusion is so large that it interferes with normal lung function. In such cases, thoracentesis may be performed to relieve the respiratory distress caused by lung compression.

An excess of pleural fluid is called an effusion. Laboratory analysis is directed at distinguishing between two types of effusion, transudates and exudates. Transudates are caused by hemodynamic changes outside the lungs that increase the movement of fluid from the capillaries in the parietal pleura into the pleural space. These include increased hydrostatic pressure (i.e., high blood pressure ); decreased oncotic pressure (i.e., low plasma protein due to liver or renal disease); increased pleural capillary permeability; and lymphatic obstruction. Exudates are caused by injury, infection, inflammation, or malignancy. Exudates usually involve the lungs, but in some cases such as esophageal rupture or pancreatitis, they do not.

A recent report suggests that thoracentesis is preferred to pericardiocentesis for pericardial and pleural effusion caused by central venous catheterization in neonates. Thoracentesis is as effective and less invasive.

Precautions

Practitioners should be aware that many pleural fluids display some characteristics of both transudates and exudates. These conditions have many causes which may be present concurrently, making the distinction complicated. The physician performing thoracentesis must take great care to avoid puncturing the lung, which can cause air to enter the pleural space (pneumothorax) and result in lung collapse. A blood sample should be collected at the time of thoracentesis to provide a basis for comparison to certain pleural fluid results. When collecting pleural fluid or blood, the physician and other members of the health care team should observe universal precautions for the prevention of transmission of bloodborne pathogens. If pH is to be measured, the syringe containing the fluid must be capped, placed in an ice bath, and sent immediately to the laboratory.

Preparation

Written consent should be obtained before the procedure is begun. X ray of the chest is performed prior to the procedure. A special view of a pleural effusion, called a lateral decubitus film, may be ordered. In this view, the patient lies down on the side on which the effusion is known to exist. If the effusion is "free-flowing," gravity will cause it to spread up the lateral chest wall. If an effusion is not free-flowing, it may be more difficult to access for thoracentesis, and ultrasound or CT guidance may be helpful. A thorough history is performed to determine if any conditions such as a bleeding disorder are present that may complicate the procedure. The history should also document the medications that the patient is currently taking, and allergies to drugs or anesthetics. Prior to the procedure, a blood sample should be collected and a platelet count and prothrombin time should be performed. These tests determine whether there is an abnormally high risk of uncontrolled bleeding from the site that may contraindicate the procedure.

Description

Generally the effusion has been identified already on chest x ray, and may be noticeable by percussion of the chest wall. Traditionally, if there has been any question about the location of the excess fluid, ultrasound or computed tomography (CT) may be used as a guide for the procedure. In recent years, studies have shown that ultrasound-guided thoracentesis results in fewer complications than thoracenteses performed with no image guidance during the procedure.

The patient should be seated upright, generally on the edge of a bed or chair, with arms propped up on a stable surface. The lateral chest wall is scrubbed with an antiseptic preparation, local anesthesia is administered, and a needle inserted between two ribs known to overlie the effusion. Generally the needle enters the chest below the armpit. Using a syringe, the appropriate amount of fluid is removed. The fluid should be collected in a heparinized syringe or transferred to a tube containing heparin or EDTA, and delivered to the lab for analysis. If the effusion is large, recurrent, or particularly concerning (e.g., very low pH and signs of infection), a chest tube may be placed and attached to a one-way system to promote continued drainage and prevent air from entering the pleural space. A pulse oximeter can be used to monitor the patient's oxygenation, and oxygen can be administered via a nasal cannula if needed. Generally oxygen therapy is not required, but if a pneumothorax occurs as a complication, or a large volume of pleural fluid is removed in a short period of time, lung function can be compromised.

Transudates form from diseases that occur outside the lungs. They are most frequently caused by congestive heart failure which accounts for up to 90% of all pleural effusions, pulmonary embolism (which sometimes causes exudates), cirrhosis of the liver, myxedema (hypothyroidism) or kidney disease. Exudates are generally due to infection, malignancy, trauma, pulmonary infarction, ruptured esophagus, pancreatitis systemic lupus erythematosus, and rheumatoid arthritis.

Sometimes bloody fluid is found in the pleural space. This may be due to major trauma that has severed blood vessels in the chest. This is termed a hemothorax, and will produce a hematocrit that approximates that of blood. Malignancies involving the pleural fluid cause an increased red blood cell count but usually do not cause massive bleeding into the pleural space. Occasionally a thoracentesis sample may appear milky (chylothorax). This can be caused by a perforated or torn thoracic duct that carries lymph from the intestines to the heart. Chylothorax can also be caused by an aggressive cancer that blocks the flow of lymph. A similar appearance to the fluid can result from necrosis, which causes formation of a pseudochylous effusion. Such fluids are characterized by foul odor, cholesterol, and high cellularity. Chylous effusions are odorless and have high triglycerides.

Malignancy is a common cause of pleural effusions and exudative fluids should always be examined for malignant cells. Approximately 35% of lung cancers, 25% of breast cancers, and 10% of lymphatic cancers shed cells into the pleural fluid.

Laboratory evaluation

Pleural fluid is generally evaluated for gross appearance and volume, protein, specific gravity, glucose, lactate dehydrogenase, blood cell counts, pH, cytology, culture and Gram stain. Other tests may be requested such as lactate, amylase, flow cytometry, triglycerides, complement, other enzymes, bilirubin, and tumor markers.

Normal pleural fluid has a volume of 3-5 mL, but effusions of several hundred milliliters are not uncommon. The fluid should be clear and light yellow (strawcolored). Turbidity can be caused by a traumatic tap or by an abnormal condition. Bloody taps are associated with streaking of the fluid as it is collected, and a clear supernatant after centrifugation. Turbidity can result from infection, mucin, or fat in the fluid. It takes very little blood to turn the pleural fluid red. In addition to a traumatic tap, red tinged fluids are caused by trauma, malignancy, and pulmonary infarction. Turbid, yellow fluids are associated with infection. Turbid, green fluids are associated with rheumatoid arthritis, and milky-white fluids with lymph containing chyle. The specific gravity of the fluid should be equal to or less than plasma. Exudates are associated with a specific gravity of 1.015 or higher, but transudates sometimes overlap this cutoff.

Chemistry tests are performed on pleural fluid by the same methods used for plasma. The pleural fluid glucose should be the same as the plasma glucose. Low levels are significant. Pleural fluid glucose below 40 mg/dL are associated with infection, malignancy, and rheumatic disease (i.e., rheumatoid arthritis) and systemic lupus erythematosus. LD is the single best test to differentiate transudates from exudates. Pleural fluid LD in excess of 200 U/L or a fluid to serum LD ratio of 0.6 or higher indicates an exudate. Lactate levels are increased in exudative fluids as well but cannot differentiate between the causes. Total protein in pleural fluid is increased when the fluid is exudative, but the interpretation is difficult whenever there is bleeding or a traumatic tap. A total protein of less than 3.0 g/dL is consistent with a transudate. Pleural fluid amylase is increased in both chronic and acute pancreatitis, in amylase producing cancers that infiltrate the pleura, and in rupture of the esophagus. pH is below 7.45 in exudative fluids and is extremely low (7.0-7.3) in malignancy, bacterial infection, rupture of the esophagus, tuberculosis, and rheumatoid arthritis. A pH below 7.0 is seen only in empyema (bacterial infection with a white count greater than 10,000 per microliter), esophageal rupture, and rheumatoid arthritis. Triglycerides are increased (greater than 110 mg/dL) in chylous effusions.

The white blood cell (WBC) count of pleural fluid is performed manually. Transudates have a WBC count of less than 1,000 per microliter. Exudates have a WBC count of 10,000 per microliter or higher. WBC counts in excess of 50,000 per microliter signal infection of the pleura. A WBC differential is always performed on pleural fluid using a method to concentrate the cells. No single cell type should predominate. A predominance of lymphocytes (greater than 50%) occurs in lymphoid cancers (lymphoma), lymphocytic leukemias, and tuberculosis. Greater than 50% neutrophils occurs in acute infections, acute injuries (such as pulmonary infarction and rupture of the esophagus), malignancies, and granulocytic leukemia. Increased eosinophils are seen in pneumothorax, pulmonary infarction, congestive heart failure, parasitic infestation, and some infections. Red blood cell counts are also performed manually. Red counts in excess of 100,000 per microliter are associated with trauma, malignancy, and pulmonary infarctions.

A Gram stain and culture should be performed on the sediment of all pleural fluids. The Gram stain of sediment is positive in about 50% of persons with pleural infections. Cultures for tuberculosis are frequently requested because this disease is associated with approximately 8% of pleural fluid effusions. Cultures should be performed using blood agar plates, chocolate (heated blood) agar plates, and thioglycolate broth. Transudative fluids are usually negative for growth. The most common bacterial isolates are Staphylococcus aureus and gram negative bacilli.

Cytological analysis of pleural fluid is usually requested and should be performed on a concentrate of any fluid that is exudative. As with microbiological culture, the sensitivity of cytology is proportional to the volume of fluid concentrated. Metastatic carcinoma, sarcomas, mesothelioma, and Hodgkin's and non-Hodgkin's lymphomas and leukemias can cause cellular infiltration of the pleura and produce exudative effusions. Activated and phagocytic mesothelial cells are often seen in inflammatory pleural fluids, and are difficult to distinguish from malignant mesothelial cells. Cytology is performed on both Wright and Papanicolaou stains. Special cytochemical stains and flow cytometry are often used to differentiate reactive from malignant mesothelial cells and identify the type of other malignant cells present.

Aftercare

Vital signs are assessed every fifteen minutes until stable. A chest x ray is ordered to document changes in the appearance of the lung fields, and to look for possible pneumothorax. Examination of the chest with a stethoscope is also useful for documenting bilateral breath sounds that make pneumothorax unlikely. The site of the needle puncture is covered with a simple dressing and monitored for bleeding or drainage.

Complications

With any procedure which breaks the skin, bleeding and infection are possibilities, although unlikely if careful and sterile technique are followed. Pneumothorax is a very real complication, and may need to be treated with a chest tube. If very large effusions are drained quickly, pulmonary edema and low oxygen levels can occur, requiring oxygen and possibly other support measures for the patient. A chest x ray should be ordered right after the procedure. If the pH and glucose are very low (e.g., pH below 7.2), white blood cells are found to be greater than 25,000 per microliter, or there are other signs of frank infection, a chest tube may need to be placed.

Results

Representative normal values for pleural fluid are shown below:

  • Volume: less than 10 mL.
  • Appearance: clear, light yellow.
  • Specific gravity: less than 1.015.
  • Protein: less than 3.0 g/dL.
  • Lactate dehydrogenase: less than or equal to 200 U/L.
  • Pleural fluid:serum LD ratio: less than 0.6.
  • pH: 7.65 (transudates 7.4-7.5).
  • Glucose: greater than 60 mg/dL (pleural fluid:serum ratio greater than 0.5).
  • Triglycerides: 13-107 mg/dL.
  • WBC count: less than 1,000 per microliter.
  • Neutrophils: less than 50%.
  • Lymphocytes: less than 50%.
  • Eosinophils: less than 10%.

Health care team roles

A physician performs the thoracentesis, and orders and interprets the results of the laboratory tests. Nursing staff will be involved in documenting a patient's response to the procedure, and providing support and instruction for the patient during thoracentesis. Careful observation of respiratory status and pulse oximetry is important to aid in speedy intervention if necessary. Clinical laboratory scientists/medical technologists perform all of the laboratory tests done on the pleural fluid with the exception of cytological evaluation, which is performed by a pathologist. Radiologic technologists will perform x rays and other imaging studies before and after thoracentesis.

KEY TERMS

Pulse oximeter— A non-invasive device that uses a beam of light that passes through a digit or earlobe to assess oxygenation.

Supernatant— A liquid that overlies material that has settled or been centrifuged; it usually is clear.

Resources

BOOKS

Light, Richard W. "Disorders of the Pleura, Mediastinum, and Diaphragm." In Harrison's Principles of Internal Medicine. Edited by Kurt Isselbacher, et al. New York: McGraw-Hill, 1998.

Malarkey, Louise M., and Mary Ellen McMorrow. Nurse's Manual of Laboratory Tests and Diagnostic Procedures, 2nd ed. Philadelphia: W.B. Saunders Company, 2000: 301-303.

Tierney, Lawrence M., Stephen J. McPhee, and Maxine A. Papadakis. Current Medical Diagnosis and Treatment 2001. Lange Medical Books/McGraw-Hill, 2001: 339-343.

PERIODICALS

Miller, Karle. "Is Ultrasound-guided Thoracentesis Safer?" American Family Physician (Sept. 1, 2003): 947.

"Thoracentesis Is a Less-invasive Neonatal Approach." Heart Disease Weekly (Sept. 26, 2004): 19.

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