Thoracentesis

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Definition

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

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 Fluid or air is withdrawn.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.

— Mark A. Mitchell

(Surg.) The operation of puncturing the chest wall so as to let out liquids contained in the cavity of the chest.

Key Terms: Axilla, Catheter, Hypovolemic shock, Osmotic pressure.

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.

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?

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., 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 Claude J. 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): 1038–42.

—J. Ricker Polsdorfer, M.D.; Mark A. Mitchell, M.D.

Surgical puncture and drainage of the thoracic cavity. The procedure may be done as an aid to the diagnosis of inflammatory or neoplastic diseases of the lung or pleura, or it may be used as a therapeutic measure to remove accumulations of fluid from the thoracic cavity.

Intervention: Thoracentesis
Chest X-ray showing a left-sided pleural effusion (right side of image). This can be treated with thoracentesis.
ICD-10 code:
ICD-9 code:	34.91
Other codes:	OPCS-4.2T12.3

The illustration shows a person having thoracentesis. The person sits upright and leans on a table. Excess fluid from the pleural space is drained into a bag.

Thoracentesis (pronounced /θɔr ʌ sɪn ˈtiː sɪs/) (also known as thoracocentesis or pleural tap) is an invasive procedure to remove fluid or air from the pleural space for diagnostic or therapeutic purposes. A cannula, or hollow needle, is carefully introduced into the thorax, generally after administration of local anesthesia. The procedure was first described in 1852.

The recommended location varies depending upon the source. It is critical that the patient holds their breath to avoid piercing the lung. Some sources recommend the midaxillary line, in the ninth intercostal space.^[1]

Contents 1 Indications 2 Contraindications 3 Complications 4 Interpretation of pleural fluid analysis 4.1 Transudate versus exudate 4.2 Amylase 4.3 Glucose 4.4 pH 4.5 Triglyceride and cholesterol 4.6 Cell count and differential 4.7 Cultures and stains 4.8 Cytology 5 References 6 External links

Indications

This procedure is indicated when unexplained fluid accumulates in the chest cavity outside the lung. In more than 90% of cases analysis of pleural fluid yields clinically useful information. If a large amount of fluid is present, then this procedure can also be used therapeutically to remove that fluid and improve patient comfort and lung function.

The most common causes of pleural effusions are cancer, congestive heart failure, pneumonia, and recent surgery. In countries where tuberculosis is common, this is also a common cause of pleural effusions.

When cardiopulmonary status is compromised (i.e. when the fluid or air has its repercussions on the function of heart and lungs), due to air (significant pneumothorax), fluid (pleural fluid) or blood (hemothorax) outside the lung, then this procedure is usually replaced with tube thoracostomy, the placement of a large tube in the pleural space.

Contraindications

An uncooperative patient or a coagulation disorder that can not be corrected are absolute contraindications.

Relative contraindications include cases in which the site of insertion has known bullous disease (e.g. emphysema), use of positive end-expiratory pressure (PEEP, see mechanical ventilation) and only one functioning lung (due to diminished reserve). The aspiration should not exceed 1L as there is a risk of development of pulmonary edema.

Complications

Major complications are pneumothorax (3-30%), hemopneumothorax, hemorrhage, hypotension (low blood pressure due to a vasovagal response) and reexpansion pulmonary edema.

Minor complications include a dry tap (no fluid return), subcutaneous hematoma or seroma, anxiety, dyspnea and cough (after removing large volume of fluid).

Interpretation of pleural fluid analysis

Several diagnostic tools are available to determine the etiology of pleural fluid.

Transudate versus exudate

First the fluid is either transudate or exudate.

A transudate is defined as pleural fluid to serum total protein ratio of less than 0.5, pleural fluid to serum LDH ratio < 0.6, and absolute pleural fluid LDH < 200 IU or < 2/3 of the normal serum.

An exudate is any fluid that filters from the circulatory system into lesions or areas of inflammation. It can apply to plants as well as animals. Its composition varies but generally includes water and the dissolved solutes of the main circulatory fluid such as sap or blood. In the case of blood: it will contain some or all plasma proteins, white blood cells, platelets and (in the case of local vascular damage) red blood cells.

Exudate

• hemorrhage
• Infection
• Inflammation
• Malignancy
• Iatrogenic
• Connective tissue disease
• Endocrine disorders
• Lymphatic disorders vs Constrictive pericarditis

Transudate

• Congestive heart failure
• Nephrotic syndrome
• Hypoalbuminemia
• Cirrhosis
• Atelectasis
• trapped lung
• Peritoneal dialysis
• Superior vena cava obstruction

Amylase

A high amylase level (twice the serum level or the absolute value is greater than 160 Somogy units) in the pleural fluid is indicative of either acute or chronic pancreatitis, pancreatic pseudocyst that has dissected or ruptured into the pleural space, cancer or esophageal rupture.

Glucose

This is considered low if pleural fluid value is less than 50% of normal serum value. The differential diagnosis for this is:

• rheumatoid effusion.The levels are characteristically low (<15 mg/dL).
• lupus effusion
• bacterial empyema
• malignancy
• tuberculosis
• esophageal rupture (Boerhaave syndrome)

pH

Normal pleural fluid pH is approximately 7.60. A pleural fluid pH below 7.30 with normal arterial blood pH has the same differential diagnosis as low pleural fluid glucose.

Triglyceride and cholesterol

Chylothorax (fluid from lymph vessels leaking into the pleural cavity) may be identified by determining triglyceride and cholesterol levels, which are relatively high in lymph. A triglyceride level over 110 mg/dl and the presence of chylomicrons indicate a chylous effusion. The appearance is generally milky but can be serous.

The main cause for chylothorax is rupture of the thoracic duct, most frequently as a result of trauma or malignancy (such as lymphoma).

Cell count and differential

The number of white blood cells can give an indication of infection. The specific subtypes can also give clues as to the type on infection. The amount of red blood cells are an obvious sign of bleeding.

Cultures and stains

If the effusion is caused by infection, microbiological culture may yield the infectious organism responsible for the infection, sometimes before other cultures (e.g. blood cultures and sputum cultures) become positive. A Gram stain may give a rough indication of the causative organism. A Ziehl-Neelsen stain may identify tuberculosis or other mycobacterial diseases.

Cytology

Cytology is an important tool in identifying effusions due to malignancy. The most common causes for pleural fluid are lung cancer, metastasis from elsewhere and mesothelioma. The latter often presents with an effusion. Normal cytology results do not reliably rule out malignancy, but make the diagnosis more unlikely.

References

1. ^ "Human Gross Anatomy". http://www.med.umn.edu/anatomy/6150/CD/Lecture%20Handouts%20HTML/2004%2010%20thoracic%20wall%20and%20lungs.htm. Retrieved 2007-10-22. 

• Intensive Care Medicine by Irwin and Rippe
• The ICU Book by Marino
• Procedures and Techniques in Intensive Care Medicine by Irwin and Rippe
• Pulmonary - Critical Care Associates of East Texas
• Thoracentesis from THE MERCK MANUAL, Sec. 6, Ch. 65, Special Procedures

External links

• Thoracocentesis video by the New England Journal of Medicine
• A photo gallery of thoracentesis showing the procedure step-by-step. V. Dimov, B. Altaqi, Clinical Notes, 2005. A free PDA version.
• Diagnostic Thoracentesis Virtual Cancer Centre
• Therapeutic Thoracentesis Virtual Cancer Centre

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