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 (
/ˌθɔrəsɨnˈtiːsɨs/), (from Greek, thorax + centesis, puncture) 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 hold his or her breath to avoid piercing of the lung. Some sources recommend the
midaxillary line, in the ninth
intercostal space.
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[edit]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.
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.
[edit]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.
[edit]Complications
Minor complications include a dry tap (no fluid return), subcutaneous
hematoma or
seroma, anxiety,
dyspnea and cough (after removing large volume of fluid).
The use of ultrasound for needle guidance can minimize the complication rate.
Several diagnostic tools are available to determine the
etiology of pleural fluid.
[edit]Transudate versus 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 .
An exudate is any fluid that filters from the circulatory system into lesions or areas of inflammation. Its composition varies but generally includes water and the dissolved solutes of the main circulatory fluid such as 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
Transudate
[edit]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
pseudocystthat has dissected or ruptured into the pleural space,
cancer or esophageal rupture.
This is considered low if pleural fluid value is less than 50% of normal serum value. The
differential diagnosis for this is:
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.
[edit]Triglyceride and cholesterol
The main cause for chylothorax is rupture of the
thoracic duct, most frequently as a result of trauma or malignancy (such as
lymphoma).
[edit]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.
[edit]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.
[edit]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
pleural mesothelioma. The latter often presents with an effusion. Normal cytology results do not reliably rule out malignancy, but make the diagnosis more unlikely.
[edit]References
- ^ "Human Gross Anatomy". Archived from the original on 2008-02-14. Retrieved 2007-10-22.
[edit]External links
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