lung thoracentesis puncture site and technique

Thoracentesis

also known as thoracocentesis  "pricking, puncture") or pleural tap (from the Greek πλευρά pleura or  pleuron "side, rib"), 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 performed by Morrill Wyman in 1850 and then described by Henry Ingersoll Bowditch in 1852

 "pricking, puncture") or pleural tap (from the Greek πλευρά pleura or πλευρόν pleuron "side, rib"), 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 performed by Morrill Wyman in 1850 and then described by Henry Ingersoll Bowditch in 1852.^[1]

The recommended location varies depending upon the source. Some sources recommend the midaxillary line, in the eighth, ninth, or tenth intercostal space.^[2] Whenever possible, the procedure should be performed under ultrasound guidance, which has shown to reduce complications.^[3][4][5]

Approach Considerations

Proper personnel resources should be ensured, appropriate equipment collected, and diagnostic laboratory studies preordered, as necessary.

The clinician should become comfortable with the equipment available at the facility. If necessary, an unused kit or one from an aborted procedure may be opened to permit evaluation of the components. The clinician should likewise become comfortable with the ultrasound machine and learn how to adjust key functions such as depth and overall gain.

Anxiolysis should be considered and good local analgesia provided. Thoracentesis can be fraught with patient anxiety, and pain is the most common complication. If mild sedation is being considered, intravenous (IV) medications should be administered to the patient in advance.

The patient should be positioned appropriately. Thoracentesis can be performed with the patient sitting upright and leaning over a Mayo stand or with the patient supine (via an axillary approach).

Thoracentesis (Thoracocentesis)

Thoracentesis is performed as follows. ^[11]

Bedside ultrasonography

After the patient has been positioned, ultrasonography is performed to confirm the pleural effusion, assess its size, look for loculations, and determine the optimal puncture site. Either a curvilinear transducer (2-5 MHz) or a high-frequency linear transducer (7.5-1 MHz) may be used (see the image below). The diaphragm is brightly echogenic and should be clearly identified. Its exact location throughout the respiratory cycle should be determined. It is important to select a rib interspace into which the diaphragm does not rise up at end-exhalation.

Ultrasound image using curvilinear probe. Image shows chest wall and large volume of pleural fluid.

Motion-mode (M-mode) ultrasonography can also be used to determine the depth of the lung and the amount of fluid between the chest wall and the visceral pleura (see the image below). Freely floating lung can be seen as wavelike undulations on the M-mode tracing.

Ultrasound image in M-mode showing sinusoidal wave pattern. This is created by the lung moving within the large pleural effusion during respiration. The depth of the lung and the amount of fluid between the parietal pleura (adherent to the chest wall) and visceral pleura (adherent to lung tissue) are easily measured with ultrasonography.

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Bedside ultrasonography is a useful guide for thoracentesis: It can determine the optimal puncture site, improve the administration of local anesthetics, and, most important, minimize the complications of the procedure. ^[2]

The optimal puncture site may be determined by searching for the largest pocket of fluid superficial to the lung and by identifying the respiratory path of the diaphragm (see the video below). Traditionally, this is between the seventh and ninth rib spaces and between the posterior axillary line and the midline. Bedside ultrasonography can confirm the optimal puncture site, which is then marked.

Preparation of puncture site

Standard aseptic technique is used for the remaining steps of the procedure. Sterile probe covers are available and should be used if thoracentesis is performed under real-time ultrasonographic guidance.

A wide area is cleaned with an antiseptic bacteriostatic solution. ^[12] Chlorhexidine solution is preferred for preparing the skin (see the image below); it dries faster and is far more effective than povidone-iodine solution.

A sterile drape is placed over the puncture site (see the first image below), and sterile towels are used to establish a large sterile field within which to work (see the second image below).

Sterile drape with fenestration and adhesive strip placed over puncture site, with sterile towels draping a large work area.

terile towels on the bed, creating a large sterile work space.

If the patient has loose skin or significant subcutaneous tissue, the puncture site can be optimized by using 3-inch tape to pull the skin or subcutaneous tissue out of the way before marking the spot and cleaning the puncture site.

The skin, subcutaneous tissue, rib periosteum, intercostal muscles, and parietal pleura should be well infiltrated with anesthetic (lidocaine 1-2%) (see the image below). Infiltration can also be guided by real-time ultrasonography using a high-frequency linear transducer (7.5-10 MHz).

Administering anesthesia to the skin, subcutaneous tissue, rib periosteum, intercostal muscle, and parietal pleura.

Insertion of device or catheter and drainage of effusion

If a commercially available device or a large intravenous catheter is being used, the skin should be nicked with a No. 11 scalpel blade to reduce drag as the catheter is advanced through the skin (see the image below).

Nicking the skin with scalpel to reduce skin drag as the catheter is advanced through the skin.

With aspiration initiated, the device is advanced over the superior aspect of the rib until pleural fluid is obtained (see the image below). The neurovascular bundle is located at the inferior border of the rib and should be avoided.

Advancing the device over the superior aspect of the rib.

Most commercial devices have a marker at 5 cm (see the image below). At this depth, the hemithorax is usually entered, and the needle need not need be advanced any further.

The 5-cm mark is at the level of the skin

The catheter is then fed over the needle introducer (see the first image below). In most cases, it can be fed all the way to the hub (see the second image below).

Feeding the catheter over the needle introducer.

The catheter is fed all the way to the hub.

With either a syringe pump or a vacuum bottle, the pleural effusion is drained until the desired volume has been removed for symptomatic relief or diagnostic analysis (see the image below).

Use the manual syringe pump method or a vacuum bottle. The syringe pump method (shown here) is more labor intensive and can cause thumb neurapraxia in the operator.

Completion of procedure

The catheter or needle is carefully removed, and the wound is dressed. If there is any doubt, pleural fluid should be sent for diagnostic analysis (see below); in practice, diagnostic analysis is almost always necessary. The patient is repositioned as appropriate for his or her comfort and respiratory status.

Finally, a procedure note is written, commenting specifically on the descriptive characteristics of the pleural fluid.

Laboratory Medicine Summary

Diagnostic analysis of pleural fluid

Pleural fluid is labeled and sent for diagnostic analysis. If the effusion is small and contains a large amount of blood, the fluid should be placed in a blood tube with anticoagulant so that it does not clot. The following laboratory tests should be requested:

• pH level
• Gram stain, culture
• Blood cell count and differential
• Glucose level, protein levels, and lactic acid dehydrogenase (LDH) level
• Cytology
• Creatinine level if urinothorax is suspected (eg, after an abdominal or pelvic procedure)
• Amylase level if esophageal perforation or pancreatitis is suspected
• Triglyceride levels if chylothorax is suspected (eg, after coronary artery bypass graft [CABG], especially if the inferior mesenteric artery [IMA] was used; milky appearance is not sensitive)

Exudative pleural fluid can be distinguished from transudative pleural fluid by looking for the following characteristics (exudates have 1 or more of these characteristics, whereas transudates have none):

• Fluid/serum LDH ratio ≥0.6
• Fluid/serum protein ratio ≥0.5
• Fluid LDH level within the upper two thirds of the normal serum LDH level

Overview

What is thoracentesis?

What are the indications of thoracentesis?

What are the contraindications of thoracentesis?

What has been shown to reduce the risk of complications following thoracentesis?

What are the major complications of thoracentesis?

What are the minor complications of thoracentesis?

Periprocedural Care

What should be included in patient education prior to consent for thoracentesis?

What risks should be discussed with patients prior to thoracentesis?

Which medical devices are designed for performing thoracentesis?

What equipment is needed to perform thoracentesis?

What is the role of anesthesia in patient preparation for thoracentesis?

What is the proper positioning of patients undergoing thoracentesis?

Technique

What is included in the preoperative preparation for thoracentesis?

What is the role of ultrasonography during the performance of thoracentesis?

How is the puncture site prepared in thoracentesis?

How is the device or catheter inserted and drainage of effusion accomplished in thoracentesis?

Laboratory Medicine

Which lab tests are performed in the diagnostic analysis of pleural fluid of thoracentesis?

How are exudative pleural fluids differentiated from transudative pleural fluids 

following thoracentesis?

Contents

• 1Indications
• 2Contraindications
• 3Complications
  • 3.1Follow-up Imaging
• 4Interpretation of pleural fluid analysis
  • 4.1Transudate versus exudate
  • 4.2Amylase
  • 4.3Glucose
  • 4.4pH
  • 4.5Triglyceride and cholesterol
  • 4.6Cell count and differential
  • 4.7Cultures and stains
  • 4.8Cytology
• 5References
• 6External links

Indications

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.

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[edit]

An uncooperative patient or a coagulation disorder that cannot be corrected are relative contraindications.^[7] Routine measurement of coagulation profiles is generally not indicated, however; when performed by an experienced operator "hemorrhagic complications are infrequent after ultrasound-guided thoracentesis, and attempting to correct an abnormal INR or platelet level before the procedure is unlikely to confer any benefit."^[8]

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). Traditional expert opinion suggests that the aspiration should not exceed 1L to avoid the possible development of pulmonary edema, but this recommendation is uncertain as the volume removed does not correlate well with this complication.^[5]

Complications[edit]

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).

The use of ultrasound for needle guidance can minimize the complication rate.^[3][4][5]

Follow-up Imaging[edit]

While chest X-ray has traditionally been performed to assess for pneumothorax following the procedure, it may no longer be necessary to do so in asymptomatic, non-ventilated persons given the widespread use of ultrasound to guide this procedure.^[9]

Interpretation of pleural fluid analysis[edit]

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

Transudate versus exudate[edit]

See also: Light's criteria

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.

An exudate 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

• 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[edit]

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[edit]

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[edit]

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[edit]

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[edit]

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.

Cytolog

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.