Thoracentesis 

Background

Thoracentesis (thoracocentesis) is a core procedural skill for hospitalists, critical care physicians, and emergency physicians. With proper training in both thoracentesis itself and the use of bedside ultrasonography, providers can perform this procedure safely and successfully.^{[1, 2]} Before the procedure, bedside ultrasonography can be used to determine the presence and size of pleural effusions and to look for loculations. During the procedure, it can be used in real time to facilitate anesthesia and then guide needle placement.

Indications

Thoracentesis is indicated for the symptomatic treatment of large pleural effusions (see the images below) or for treatment of empyemas. It is also indicated for pleural effusions of any size that require diagnostic analysis.^[3]

Transudative effusions result from decreased plasma oncotic pressures and increased hydrostatic pressures. Heart failure is by far the most common cause, followed by liver cirrhosis and nephrotic syndrome.

Exudative effusions result from local destructive or surgical processes that cause increased capillary permeability and subsequent exudation of intravascular components into potential spaces. Causes are manifold and include pneumonia, empyema, cancer, pulmonary embolism, and numerous infectious etiologies.

Contraindications

There are no absolute contraindications for thoracentesis. Relative contraindications include the following:

• Uncorrected bleeding diathesis
• Chest wall cellulitis at the site of puncture

Patient Education/Informed Consent

Before thoracentesis, it is important to pay attention to the consent process and provide a focused set of risks and complications, so that the patient is not surprised if he or she experiences adverse effects.^[4]

Consent should be obtained from the patient or family member. The reason the procedure is being performed (suspected diagnosis); the risk, benefits, and alternatives of the procedure; the risks and benefits of the alternative procedure; and the risk and benefits of not undergoing the procedure. Allow the patient the opportunity to ask any questions and address any concerns they may have. Make sure that they have an understanding about the procedure so they can make an informed decision.

The patient should be counseled about the risks of pneumothorax, hemothorax, lung laceration, infection, empyema, damage to the intercostals, or internal mammary vessels, diaphragmatic injury, puncture of the liver or spleen, damage to other abdominal organs, abdominal hemorrhage, reexpansion pulmonary edema, air embolism, cough, pain, and catheter fragment left in the pleural space.

Discuss how these risks can be avoided or prevented (eg, proper positioning, ensuring that the patient remains as still as possible during the procedure, adequate analgesia).

Equipment

Several commercially available medical devices are specifically designed for performing thoracentesis. Such devices include the following:

• Arrow-Clarke Thoracentesis Device (Teleflex Medical, Research Triangle Park, NC)
• Argyle Turkel Safety Thoracentesis System (Covidien, Mansfield, MA)
• Critical Care Thoracentesis Set (Cook Medical, Bloomington, IN)

If a commercial use-specific device is not available, all of the necessary equipment can be obtained from the supplies located in most inpatient settings, critical care units (CCUs), or emergency departments (EDs).

• Thoracentesis device - This typically consists of an 8-French catheter over an 18-gauge, 7.5-in. (19-cm) needle with a 3-way stopcock and, ideally, a self-sealing valve
• Self-assembled device, if a thoracentesis device is unavailable - Options include using an 18-gauge needle or a 12-gauge intravenous (IV) catheter connected to a 60-mL syringe and then to a stopcock after the needle is removed from the 60-mL syringe
• Injection needle – 22 gauge, 1.5 in. (3.81 cm)
• Injection needle – 25 gauge, 1 in. (2.54 cm)
• Luer-Lok syringe - 10 mL
• Luer-Lok syringe - 5 mL
• Luer-Lok syringe - 60 mL
• Tubing set with aspiration/discharge device
• Antiseptic - Chlorhexidine solution [Hibiclens] is preferred
• Lidocaine - 1% or 2% solution, 10-mL ampule
• Specimen cap for 60-mL syringe
• Specimen vials or blood tubes
• Drainage bag or vacuum bottle
• Drape - 24 × 30 in., with 4-in. fenestration with adhesive strip
• Sterile towels
• Scalpel - No. 11 blade
• Adhesive dressing - 7.6 × 2.5 cm
• Gauze pad(s) - 4 × 4 in.

Patient Preparation

Patient preparation includes adequate anesthesia and proper positioning.

Anesthesia

In addition to local anesthesia, mild sedation may also be considered. IV midazolam or lorazepam can attenuate the anxiety that may be associated with any invasive procedure. Analgesia is critically important, in that pain is the most common complication of thoracentesis. Local anesthesia is achieved with generous local infiltration of lidocaine.

The skin, subcutaneous tissue, rib periosteum, intercostal muscle, and parietal pleura should all be well infiltrated with local anesthetic. It is particularly important to anesthetize the deep part of the intercostal muscle and the parietal pleura because puncture of these tissues generates the most pain. Pleural fluid is often obtained via aspiration during anesthetic infiltration of these deeper structures; this helps confirm proper needle location.

Positioning

Patients who are alert and cooperative are most comfortable in a seated position (see the image below), leaning slightly forward and resting the head on the arms or hands or on a pillow, which is placed on an adjustable bedside table. This position facilitates access to the posterior axillary space, which is the most dependent part of the thorax. Unstable patients and those who are unable to sit up may be supine for the procedure.

The patient is moved to the extreme side of the bed, the ipsilateral hand is placed behind the head, and a towel roll is placed under the contralateral shoulder. This measure facilitates dependent drainage and provides good access to the posterior axillary space.

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.^[5]

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.

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.

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 7th and 9th 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.^[6] 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).

If the patient has loose skin or significant subcutaneous tissue, the puncture site can be optimized by using 3-in. 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).

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).

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.

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 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).

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).

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.

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
• 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

Complications of Procedure

Complication rates for thoracentesis performed by experienced clinicians are not available. However, data on complications that develop after thoracentesis performed by residents learning the procedure are available.^{[7, 1]}

Major complications include the following:

• Pneumothorax (11%^[8] )
• Hemothorax (0.8%)
• Laceration of the liver or spleen (0.8%)
• Diaphragmatic injury
• Empyema
• Tumor seeding

Minor complications include the following:

• Pain (22%)
• Dry tap (13%)
• Cough (11%)
• Subcutaneous hematoma (2%)
• Subcutaneous seroma (0.8%)
• Vasovagal syncope