Chapter 40. Thoracentesis

Thoracentesis is a term derived from the Greek meaning “to pierce the chest.” It is used today to refer to the removal of air or fluid from the thoracic cavity. Accumulation of pleural fluid is not a specific diagnosis but rather a reflection of an underlying process. In almost all newly discovered pleural effusions, thoracentesis should be performed to aid in the diagnosis and management of the underlying etiology.

Hippocrates first described thoracentesis in the management of an empyema.1 Thoracentesis was used widely in World War II and the Korean conflict in lieu of a thoracotomy for chest drainage. By the time of the Vietnam War, this practice was replaced by tube thoracostomy. Today, thoracentesis is used in the diagnosis and therapy of pleural effusions, emergent and temporizing treatment of a tension pneumothorax, and the management of small, nontraumatic pneumothoraces.1–4

A pleural effusion can be identified clinically and radiologically. Clinically, the patient may develop pain related to irritation of the parietal pleura, compromised pulmonary mechanics, or interference with gas exchange.3 The pain may be located in the chest, abdomen, or ipsilateral shoulder. Another common symptom is a cough; its mechanism is unclear. Dyspnea occurs secondary to the space-occupying effect of the fluid and alterations in gas exchange. In extreme cases, pleural effusions can reduce cardiac output. On physical examination, tactile fremitus is absent or attenuated and there is dullness to percussion. Auscultation reveals decreased breath sounds on the involved hemithorax.

Radiographically, on a posteroanterior (PA) chest radiograph, an effusion can be diagnosed when there is homogeneous opacification in the hemithorax, absent air bronchograms, and clouded vesicular vascular markings. In a cadaveric study, the minimum fluid volume needed to blunt the costophrenic angle was 175 mL.5 More than 500 mL had to be injected into some cadavers to blunt the costophrenic angle.5 In a study on mechanically ventilated patients, ultrasound consistently identified nonloculated pleural effusions when the effusion was at least 500 mL.6 A lateral decubitus film is often necessary and will determine whether the fluid is loculated or free-flowing. It will also be helpful if one of the following signs is present on the PA chest radiograph: a clear costophrenic angle, an elevated hemidiaphragm, a blurred contour of the diaphragmatic dome, or the gastric bubble seen more than 2 cm from the lung border in patients with left-sided pleural effusions.2 If the fluid collection is 10 mm thick on the lateral decubitus film, thoracentesis can most likely be performed using clinical skills to locate the fluid.7 If it is less than 10 mm thick, ultrasound may be needed for localization.3

The use of ultrasound is no longer limited to Radiologists. With proper training, Emergency Physicians can utilize ultrasound for thoracentesis procedural guidance. The portable AP (anteroposterior) radiograph cannot always reliably distinguish between a pleural effusion, a pneumonia, or atelectasis.8 In these indeterminate cases, ultrasound can be clinically useful. Pleural fluid can be identified as a black hypoechoic area, which appears darker than the surrounding lung, diaphragm, and liver. Ultrasound can aid in the identification of small effusions. Thoracentesis performed blindly has an associated complication rate of up to 30%.9 Ultrasound allows the Emergency Physician to map the pleural effusion and choose the best site for thoracentesis, thereby reducing the rate of pneumothoraces to less than 3%.10–14 Ultrasound guidance has been shown to be very safe in assisting with thoracentesis in intubated and mechanically ventilated patients, both high-risk populations for complications.12,15

A pneumothorax may be simple or under pressure (also known as tension). A simple pneumothorax may present clinically with chest pain, dyspnea, hypoxia, and tachycardia. Physical examination may reveal, on auscultation, decreased breath sounds on the affected side. Performance of a thoracentesis to relieve a tension pneumothorax is based on the mechanism of lung injury, the patient's symptoms, and physical examination findings. Mechanisms of injury to the lung include mechanical ventilation, chest trauma, instrumentation of the chest, and spontaneous lung rupture. Classically, the patient has a clinical presentation of hypotension, tachycardia, and absent breath sounds on the affected side. Other symptoms may include a deviated trachea, acute change in mental status, air hunger, chest pain, cyanosis, diaphoresis, hypoxia, and cardiorespiratory arrest.1,4 Sometimes a patient with a tension pneumothorax may have a normal physical examination due to subtle auscultation findings often missed in a noisy Emergency Department. Tactile fremitus may be absent and percussion is typically hyperresonant over the hemithorax with the tension pneumothorax.

There are two major indications for performing a thoracentesis.1–3,6 The first is for the evacuation of air. This includes a simple pneumothorax and the emergent diagnosis and temporizing treatment of a tension pneumothorax. The second is for the evacuation of fluid. This may be done to help diagnose the etiology of pleural effusion or for the treatment of a symptomatic pleural effusion.

Anatomy and Pathophysiology

The pleura is a serous membrane that covers the lungs, mediastinum, diaphragm, and thoracic cavity. The pleural space is a potential space between the lung and the thoracic cavity. A thin layer of fluid normally exists between the visceral pleura covering the organs and the parietal pleura covering the chest wall. This fluid acts as a lubricant.3 Pleural fluid originates from three sources: parietal capillaries, visceral capillaries, and the interstitium. Hydrostatic and oncotic forces govern the flow of fluid in the pleural space. These forces are summarized in Figure 40-1. In a healthy person, protein-free fluid enters the pleural space from the parietal pleura and is absorbed by the visceral pleura. Small amounts of protein then leak into the pleural space. Approximately 10% of the pleural fluid and large proteins are removed by the lymphatics at a rate of up to 20 mL/h for each hemithorax.2 Ventilation and muscular activity facilitate the action of the lymphatics.3

Alterations in pleural fluid homeostasis will lead to a pleural effusion: a pathologic collection of excess fluid, located between the visceral and parietal pleura. Hydrostatic changes result in protein-free effusions (transudates). Changes in oncotic pressure (abnormality in the lung or pleura) lead to effusions. The differential diagnosis of transudates and exudates is listed in Table 40-1.

Indications

A thoracentesis may be performed to remove pleural fluid for analysis to diagnose the etiology of the fluid (e.g., malignancy, infection). It may also be performed to relieve the patient's symptom of dyspnea when a large pleural effusion interferes with normal respiration or results in respiratory compromise.

Contraindications

The only absolute contraindications are an uncooperative patient or a patient who refuses to give informed consent for the procedure.16 Uncooperative patients or patients with altered levels of consciousness may require sedation for the procedure.

There are numerous relative contraindications to performing a thoracentesis. Patients receiving anticoagulants, with a bleeding diathesis (whether known or suspected), or thrombocytopenia have a significant risk of bleeding.2,16 Consider reversing the anticoagulant or the bleeding disorder prior to performing the thoracentesis. A small volume of pleural fluid may make the procedure difficult to perform and increase the risk of complications.16 Patients undergoing positive-pressure ventilation (i.e., mechanical ventilator, BiPAP, or CPAP) are at an increased risk of developing a pneumothorax and a tension pneumothorax.1 Although, one study has shown that a thoracentesis can be done as safely in a ventilator-dependent patient as in patients not being mechanically ventilated.17 Pleural adhesions may limit the amount of fluid obtained or require multiple thoracenteses to drain the fluid.1 Loculated pleural adhesions should be drained under ultrasound guidance. Areas of cellulitis or other infection on the chest wall should be avoided unless no alternate site can be identified for the procedure.1,3 Unsupervised physicians with little or no experience should not perform this procedure, as the risk of complications is increased.7 Patients with chronic obstructive pulmonary disease are at increased risk for complications.

Equipment

Diagnostic Thoracentesis for Pleural Effusions

• Sterile gloves and gown
• Face mask with a face shield or goggles
• Local anesthetic solution, 1% to 2% lidocaine
• Heparin, 1000 U/mL
• Atropine, 1 mg
• Alcohol pads
• Povidone iodine or chlorhexidine solution
• Gauze 4 × 4 squares
• Sterile drapes
• Sterile towels
• Sterile gloves
• Band-aids
• 25 or 27 gauge needle
• 21 and 22 gauge needles, 1.5 in. long
• 10 mL syringes
• 50 mL syringe
• 18 or 20 gauge needle

Ultrasound Guidance

• Ultrasound machine
• 3.5 to 5.0 MHz phased-array ultrasound probe
• Sterile ultrasound gel
• Sterile ultrasound probe cover

Therapeutic Thoracentesis for Pleural Effusions

• The supplies listed above
• 16 to 18 gauge catheter-over-the-needle
• 14 to 18 gauge catheter-through-the-needle
• Three-way stopcock
• Connector tubing (connects to three-way stopcock and sterile container)
• Sterile container for pleural fluid
• 50 mL syringe
• Intravenous extension tubing

Commercial kits have been developed and are available to provide the equipment needed to perform a thoracentesis. The kits are disposable, intended for single-patient use, and contain the required equipment. They save time in that the equipment does not have to be found and set up. Disadvantages include potential increased cost and limited equipment in the kit.18 Common kits include the Pharmaseal, distributed by Baxter (Jacksonville, TX); the Arrow Clark Thoracentesis Kit, distributed by Arrow (Reading, PA); the Argyle Turkel Safety Thoracentesis Kit, distributed by Boston Scientific (Miami, FL), and the Turkel Thoracentesis Kit, distributed by Tyco Healthcare (Mansfield, MA).3

Patient Preparation

Explain the procedure, its risks, and benefits to the patient and/or their representative and obtain a signed consent form.1 The position of the patient can vary depending on their clinical condition. Patients who are ambulatory and cooperative should sit up at the edge of a bed with their feet on the floor or a stool (Figure 40-2). Place the patient's head and arms on an elevated bedside tray. The patient's back should be as vertical as possible so that the lowest part of the hemithorax is posterior. This will ensure that the free-flowing fluid remains posteriorly.1–3,16

In debilitated patients, one of three other positions is recommended. Place the patient in the lateral decubitus position, lying on the side of the pleural effusion. The patient's back should be along the edge of the bed. The procedure would then be performed in the midscapular line or the posterior axillary line. Place a ventilator-dependent patient into the lateral decubitus position, lying on the side with the pleural effusion.17 Second, place the patient supine and elevate the head of the bed as much as maximally possible. The patient would then be sitting with the assistance of the bed, and the procedure would be performed in midaxillary or posterior axillary line.3 Finally, the patient can be placed supine. The procedure would then be performed at the posterior or midaxillary line. With the patient supine, ultrasonography may be required to locate the pleural fluid. Sedation or paralysis may be needed for optimal positioning depending on the patients clinical condition.

After positioning the patient, clean any dirt or debris from the skin. Identify the anatomic landmarks required to perform the procedure. After viewing the chest radiograph and estimating the amount of pleural fluid, percuss from superior to inferior starting at the midscapular or posterior axillary line. The site chosen for aspiration should be a single interspace below the top of the dullness to percussion.

If the fluid thickness is less than 10 mm on radiographs, ultrasound may be used to locate the fluid.5,16 Alternatively, ultrasound can be routinely used to locate pleural fluid. Ultrasound has been shown to be comparable to CT for diagnosing and managing a pleural effusion.19

Although not required, some Emergency Physicians place the patient on the cardiac monitor, noninvasive blood pressure cuff, pulse oximetry, and supplemental oxygen to monitor them during and after the procedure. Apply povidone iodine or chlorhexidine solution to the skin surface and allow it to dry. Apply sterile drapes around the site of the procedure. If using an ultrasound-guided technique, be sure to fit the transducer with a sterile glove or probe cover before exposing the probe to the sterile skin. Use sterile ultrasound gel. Atropine should be at the bedside. It can be administered (1.0 mg subcutaneously or intramuscularly or 0.5 mg intravenously) to patients who develop symptomatic bradycardia during the procedure. The Emergency Physician should wear full personal protective equipment to protect themselves from contact with the patient's blood and body fluids as well as protect the patient from infection.

Place a skin wheal of local anesthetic solution over the thoracentesis site using a 25 or 27 gauge needle on a 10 mL syringe containing the local anesthetic solution. Remove the 25 or 27 gauge needle from the syringe. Apply a 21 or 22 gauge, 1.5 to 3.0 in needle to the syringe containing the local anesthetic solution. Anesthetize the subcutaneous tissues and the periosteum of the rib (Figure 40-3). Walk the needle up the rib while simultaneously injecting local anesthetic solution. Gently aspirate prior to injecting each time the needle is advanced to ensure that the needle is not within a blood vessel. When the superior border of the rib is located, slowly and carefully advance the needle over the rib while applying negative pressure on the syringe. Be sure not to insert the needle below the rib to avoid injury to the neurovascular bundle inferior to the rib. When the pleural space has been entered, fluid will flow into the syringe. Inject and aspirate small volumes (1 to 2 mL) while the needle is within the pleural cavity. This will distribute the local anesthetic solution into the pleural fluid and ensure anesthesia of the pleura. Withdraw the needle from the pleural cavity and out the skin.

Diagnostic Thoracentesis Technique for Pleural Effusions

Attach an 18 gauge needle to a 50 mL syringe containing 1 mL of heparin. The heparin will ensure accurate pH and cell counts as it prevents the fluid from clotting. Introduce the needle through the anesthetized track and into the pleural cavity (Figure 40-4B). Aspirate up to 50 mL of fluid. Withdraw the needle and place the fluid into the appropriate sterile containers. Use proper techniques when transferring the fluid into containers or specimen tubes to prevent a needlestick injury.

If pleural fluid cannot be aspirated, also known as a dry tap, four possibilities must be considered. The needle may be too short, positioned too high to reach the fluid (Figure 40-4A), positioned too low to reach the fluid (Figure 40-4C), or there may not actually be an effusion. Repeat the physical examination and review the chest radiograph to reconfirm the presence of a pleural effusion. Use ultrasound, if available, to assess the presence of a pleural effusion. Penetration of the lung with the needle is rarely catastrophic but can result in a pneumothorax.3

For debilitated patients, the principles are the same with the exception of the site for the procedure. If the patient is supine, use the midaxillary line or the posterior axillary line. Be cautious of the diaphragm, as it can be as high as the fifth interspace on expiration at the anterior axillary line. If the patient is in the lateral decubitus position, use the midscapular line or the posterior axillary line for the procedure.

Therapeutic Thoracentesis Techniques for Pleural Effusions

The same sterile preparation, location of fluid, positioning, and anesthesia considerations apply for therapeutic thoracentesis as with the diagnostic procedures. However, there is one difference between a diagnostic and a therapeutic thoracentesis—that is, the quantity of fluid removed. Up to 1.5 L is removed in a therapeutic thoracentesis. A diagnostic thoracentesis requires approximately 10 to 20 mL of pleural fluid.

Catheter‐over‐the-Needle Technique

Two types of catheters can be used to perform this procedure. They are the catheter-over-the-needle and the catheter-through-the-needle (Figures 40-5 & 40-6). The catheter-over-the-needle technique is most commonly used (Figure 40-5). Make a small “nick” in the skin with a #11 surgical blade at the needle insertion site. Attach a 14 to 18 gauge catheter-over-the-needle to a 10 mL syringe as a handle. Insert the catheter-over-the-needle into the nick and advance it, reproducing the original anesthetized tract (Figure 40-5A). Apply negative pressure to the syringe as the catheter-over-the-needle is advanced. Stop advancing the catheter-over-the-needle when fluid is aspirated. Angle the catheter-over-the-needle caudally. Securely hold the syringe and needle so they do not move. Advance the catheter until the hub is against the skin. Withdraw the needle and syringe as a unit while the catheter remains in the pleural cavity (Figure 40-5B). When the needle is removed, quickly cover the catheter with a gloved finger. This will prevent ambient air from entering the pleural cavity. Attach intravenous catheter extension tubing to the hub of the catheter. Place a three-way stopcock attached to a 50 mL syringe onto the extension tubing. Hold the catheter hub against the skin securely. Aspirate fluid into the syringe and then advance the fluid into the sterile container by adjusting the three-way stopcock.

An alternative option is to set up a siphon through the three-way stopcock. Prime the tubing with pleural fluid. Place the end of the tubing into a sterile container that is located below the site of the catheter. This allows the fluid to flow freely into the sterile container. Fluid can be removed in 50 mL aliquots up to 1.5 L. As a general rule, this is the limit, due to the risk of postevacuation pulmonary edema and excessive protein loss.1

Catheter‐Through‐the-Needle Technique

The second option is to utilize the catheter-through-the-needle system (Figure 40-6), known as the Bardig Intracath system. It is not as popular as the catheter-over-the-needle systems. Place the needle on a tuberculin syringe. Insert the needle and advance it through the anesthetized tissues (Figure 40-6A). A small “nick” in the skin with a #11 surgical blade will facilitate needle entry. Apply negative pressure to the syringe as the needle is advanced along the anesthetized tract and into the pleural cavity (Figure 40-6A). Stop advancing the needle when fluid is aspirated. Securely hold the needle so it does not move. Remove the syringe and cover the needle hub with a gloved finger. This will prevent ambient air from entering the pleural cavity. Angle the needle slightly caudally and advance the catheter through the needle (Figure 40-6B). Withdraw the needle, leaving the catheter within the pleural cavity (Figure 40-6C). Once the needle is removed, do not readvance the needle, as the catheter may shear off and fall into the pleural cavity. Place a three-way stopcock or a large syringe onto the hub of the catheter. Place the needle guard on the needle. Secure the catheter by taping it to the skin. Withdraw fluid as previously described. Fluid can be removed in 50 mL aliquots up to 1.5 L. As a general rule, this is the limit, due to the risk of postevacuation pulmonary edema and excessive protein loss.1

Seldinger Technique

An alternative approach is to use the Seldinger technique to insert a small bore catheter into the pleural cavity. The major disadvantages to this technique include the time it takes to insert the catheter, the cost of the catheter kit versus a catheter-over-the-needle, and catheter blockage (from cells, debris, and protein) requiring insertion of a second catheter. Another option is to use a central venous catheter kit.20,21 The larger catheter opening may not become obstructed as easily.

Ultrasound-Guided Technique for Pleural Effusions

Ultrasound can be used to map the location and the extent of pleural effusion, and to help identify the appropriate site of needle entry. Real-time guidance is usually not required. A 3.5 to 5.0 MHz phased-array probe is recommended for ultrasound-guided examination of the pleural space.22 In general, orientation of the probe follows the convention that the probe marker should correlate to the reference point in the left upper corner of the screen.

With the patient in an upright sitting position, percuss and auscultate the posterior thorax to estimate the location of pleural fluid. Apply sterile ultrasound gel onto the ultrasound probe cover. Place the probe at the intercostal space of the estimated level of pleural fluid in the posterior axillary line, usually at the level of ribs 9 to 11. Sweep the probe superiorly and inferiorly, as well as transversely, to assess the location and size of the fluid collection. Identify the liver on the right, the spleen on the left, and the diaphragm.

In a debilitated patient in the lateral decubitus position, place the ultrasound probe in the midscapular line or, if possible, the posterior axillary to locate the fluid. A ventilator-dependent patient should be placed in the lateral decubitus position. If the patient is supine, place the probe in the posterior or midaxillary line. The real-time movement of the diaphragm can be used as a key reference point when examining the pleural space.23 The liver may also be used as a echogenic reference point for the identification of adjacent hyperechoic or hypoechoic structures. Keep in mind that the best window to view the intrathoracic contents is through the intercostal space, as ultrasound penetration through the soft tissue is superior to that of bone.

The ultrasound waves will initially penetrate the skin, subcutaneous tissue, and muscle to produce multiple layers of varying echogenicity. The echogenic ribs cast an acoustic shadow (Figure 40-7). The parietal and visceral pleura are encountered posterior to the rib as two hyperechoic lines, each <2 mm thick.23,24 The diaphragm can be identified as a hyperechoic transverse structure at the base of the chest wall. The lung is visualized as a bright, hyperechoic structure just cephalad to the diaphragm. The lung should become more intensely hyperechoic, or brighter in the inspiration phase. A pleural effusion can be identified as an anechoic to a hypoechoic image above the diaphragm that decreases in size with inspiration.

Two additional ultrasound findings should be identified on exam: “lung slide” and “comet tail” artifact. The movement of the lung in reference to the surrounding parietal pleura with inspiration and expiration produces an artifact referred to as “lung slide.” Normal inspiration should produce a “slide” with each breath, representing movement between the visceral and parietal pleural interface. The thin, hyperechoic sliding line is located approximately 0.5 cm below the surface of the rib, and should move back and forth with each inspiration.25 A “comet tail artifact” is another normal finding that can be readily identified in a healthy patient. The comet tail artifact is identified as a hyperechoic vertical artifact that slides transversely and is oriented perpendicular to the transverse “lung slide” previously mentioned.25

A pleural effusion is easily visualized using ultrasound (Figure 40-8). It appears black or anechoic. A distinct hyperechoic pleural line is not seen as the parietal and visceral pleura are separated by the effusion. Lung tissue appears hyperechogenic compared with the anechoic effusion (Figure 40-9). The pleural effusion can be seen moving during the respiratory cycle.

The posterior approach is the preferred choice in the stable, cooperative patient who is able to sit up and lean over a table (Figure 40-10). To survey the lung anatomy and map the effusion, scan the posterior hemithorax from the inferior border of the scapula to the upper lumbar region and from the paravertebral area to the posterior axillary line. Note the minimum depth of the effusion and the location of other vital structures (i.e., diaphragm, liver, spleen, and lung). Scan with the probe parallel to and perpendicular to the ribs, and observe the structures during the full respiratory phase. The diaphragm can go as low as the 12th rib posteriorly and as high as the 8th rib laterally. Determine the location of the skin entry site. Mark the site with a pen, surgical marker, or by indenting the skin with the cap of a needle. The ideal site should have a large area of pleural effusion and be free of any internal structures (i.e., liver, spleen, or diaphragm) along the needle path.

The lateral approach is used for mechanically ventilated patients and for those who are unable to sit up for the procedure. Abduct the ipsilateral arm and place the hand behind the patient's head, as one would in preparation for the placement of a chest tube (Figure 40-11). Survey the anterior and lateral thorax from the midclavicular line to the posterior axillary line. Note the depth of the effusion and the location of any vital structures to be avoided. Determine and mark the skin entry site.

The lateral decubitus approach is an alternative for patients unable to sit upright. Place the patient on their side with the pleural effusion side down. Use ultrasound to map the effusion. Note the distance from the skin to the effusion, the depth of the effusion, as well as the presence of any important structures to be avoided. Determine and mark the skin entry site, usually at the posterior axillary line.

Regardless of the patient position or approach, do not allow the patient to move once they have been scanned and the skin entry site marked. Prep and drape the patient similar to that for the blind thoracentesis approach. Use local anesthetic to anesthetize the skin, rib, and pleura. The catheter-over-the-needle can be inserted blindly, as described previously, at the skin insertion site or using real-time ultrasound guidance.

The use of ultrasound guidance can be helpful. Place a sterile cover over the ultrasound probe. Apply sterile ultrasound gel over the cover. Rescan the patient in the area previously identified the skin entry site (Figure 40-12). Verify that no structures are along the needle path between the skin and the pleural effusion. Insert an 18 gauge catheter-over-the-needle into the pleural space using the technique already described while using ultrasound for real-time visualization of the needle entering the pleural cavity. The needle will appear as a thin, bright, hyperechoic structure moving through the skin, subcutaneous tissue, parietal pleura, visceral pleura, and finally reaching the hypoechoic pleural effusion (Figure 40-13). Aspirate to confirm that the catheter-over-the-needle is within the pleural effusion. Place the ultrasound probe aside. Continue the remainder of the procedure as described previously.

Assessment

Numerous analyses of the pleural effusion fluid are required to determine its etiology (Table 40-2). Large pleural effusions are more commonly associated with infections and malignancy.26 Fluid analysis criteria have been established to separate transudates and exudates.10,27 If the fluid fits one of the criteria in Table 40-3, it is an exudate. These parameters have been confirmed to have 98% sensitivity and 83% specificity in detecting exudates.28 Color and odor can be helpful. If the fluid has a putrid odor, consider an infection. White or yellow fluid suggests an empyema or chylothorax. The fluid's white blood cell count is of limited benefit. If it is >10,000, the fluid likely represents a parapneumonic effusion. A pleural fluid hemoglobin and hematocrit can be compared to that of the blood. Bloody pleural effusions are usually associated with malignancy, pneumonia, pulmonary embolism with a lung infarction, or trauma.29 If the fluid is grossly bloody, consider a hemothorax. If the pleural fluid's hematocrit is >50% of the serum hematocrit, a hemothorax is likely and chest tube placement should be considered. Other helpful tests include a fluid pH. If the pH is below 7.25 to 7.30, consider it the result of a parapneumonic process, rheumatologic process, esophageal rupture, or malignancy. An elevated amylase level suggests esophageal rupture, malignancy, or pancreatic disease.30 Elevated triglyceride levels suggest a chylothorax. Cytology is important to search for an underlying malignancy. Up to 50% of patients with a pulmonic malignancy will have neoplastic cells in the pleural fluid.3 Bacteriologic information such as Gram's stain, acid-fast, and fungal preparations are also important, although the yield can be below 30%.16 Fluid should always be sent for aerobic and anaerobic cultures to rule out an infectious etiology for the pleural effusion. The appearance of pleural fluid on ultrasound may help identify whether the pleural fluid is a transudate or an exudate. Transudates are consistently seen as anechoic, whereas exudates may range from an anechoic to a hyperechoic.31,32

Aftercare

When done aspiring fluid, remove the catheter and apply a bandage to the puncture site. Several authors have suggested that a postprocedure chest radiograph may not be necessary.33,34 These were small studies with methodologic errors. Omitting the postprocedure chest radiograph cannot be recommended at this time. Obtain a plain chest radiograph upon completion of the procedure to assess for a pneumothorax. An expiratory film is the best film to look for a pneumothorax, especially if it is small. Repeat a chest radiograph in 4 to 6 hours to look for a delayed pneumothorax. If no pneumothorax is present and if appropriate for the clinical condition, the patient may be discharged with good instructions and close follow-up.

The procedure site should be evaluated two to three times a day for signs of infection. These patients should be educated about the signs, symptoms, and significance of an infection. They should return to their primary physician or the Emergency Department immediately if they develop fever, chills, shortness of breath, redness or pus at the puncture site, or if any concerns arise.

Complications

The potential complications of a thoracentesis are listed in Table 40-4.1,3,16,28,35 Complication rates range from 20% to 50%. The major complications are a 5% to 19% incidence of pneumothorax and a 1% to 7% incidence of pneumothorax requiring a chest tube.11,36 One author recommends ultrasound-guided thoracentesis for all patients as the safest approach, although this is disputed by others.9,36 The majority of studies report lower rates of postprocedural pneumothoraces with ultrasound-guided thoracentesis performed by an experienced operator.9–11,15,37–41 However, others have not shown a significant difference in the incidence of postprocedural pneumothoraces with the use of ultrasound.42,43

The use of the proper technique and the Emergency Physician's experience are important in reducing the rate of complications.44–46 Despite this, it is difficult to predict which patients may be at risk of developing a postprocedural pneumothorax.47 Drainage of large volumes of fluid, greater than 1.5 to 2 L, may increase the risk of developing a pneumothorax.48 Improper technique or tortuosity of the intercostal artery can result in intercostal artery injury.49 Qureshi compiled methods to reduce the incidence of pneumothorax.16 They are direct supervision of inexperienced operators, removal of small amounts of fluid, use of small-gauge needles, use of ultrasound for small effusions, and use of a needle-catheter system for a therapeutic procedure.

Anatomy and Pathophysiology

A thoracentesis can be performed to relieve a simple pneumothorax or a tension pneumothorax. A pneumothorax can be defined by the presence of air between the visceral and parietal pleura.25 Primary spontaneous pneumothoraces occur in otherwise healthy people without antecedent trauma. Secondary spontaneous pneumothoraces occur as a complication of underlying lung disease, most commonly chronic obstructive pulmonary disease.1,3 A traumatic pneumothorax occurs as a result of penetrating or blunt trauma to the thoracic cavity. An iatrogenic pneumothorax is a subcategory of the traumatic pneumothorax, with the three most common etiologies being pleural biopsy, subclavian vein catheterization, and thoracentesis.

The pressure in the pleural space is negative in reference to the atmosphere. This is due to the tendency of the lung to collapse and the chest wall to expand. The alveolar pressure is greater than the pleural space pressure due to the elastic recoil of the lung. As a result, if a communication occurs between the alveolar and pleural space, the air will preferentially move into the pleural space until the pressure equalizes. The physiologic consequence is a decrease in vital capacity and PaO2. This may be well tolerated in otherwise healthy people but not in patients with underlying cardiac and/or pulmonary disease. If a one-way valve develops such that air can only enter the pleural space from the alveolus but not return, the intrapleural pressure will eventually exceed atmospheric pressure, with a progressive increase in air occupying the pleural space. Clinical deterioration may occur due to a decreasing PaO2 and cardiac output.50–52 Other data point to hypoxia and hypercarbia as the cause of clinical deterioration.18

Ultrasound guidance may aid in locating a pneumothorax, with the best viewing window being the intercostal space. Zhang et al. showed a sensitivity and specificity of ultrasound in diagnosing a pneumothorax of 86% and 97%, respectively; whereas conventional radiography was 28% and 100%, respectively.53 In addition, ultrasound diagnosed a pneumothorax within only 2 to 5 minutes, compared to 20 to 30 minutes for chest radiography.53 In a similar study, ultrasound showed a sensitivity and specificity of 100% and 94% for detection of pneumothoraces, compared to 36% and 100% for chest radiography.54

Controversy exists to the exact management of a spontaneous pneumothorax.55–60 Options include simple aspiration, tube thoracostomy, and simple aspiration followed by a tube thoracostomy if aspiration fails. Simple aspiration is more likely to fail with larger pneumothoraces.58,59 Several recent reviews, including a Cochrane Collaboration, came to similar conclusions regarding simple aspiration.55–57 These conclusions, while not definitive, were that simple aspiration is associated with a reduction in the percentage of patients requiring hospitalization compared to tube thoracostomy. There were no differences between the two procedures in early failures, immediate success rate, duration of hospitalization, one-year success rates, and the number of patients requiring a subsequent pleurodesis. Advantages of simple aspiration compared to tube thoracostomy include less equipment costs, easier to perform, simpler to perform, quicker to perform, and the potential to avoid hospitalization.

Indications

All tension pneumothoraces require needle drainage followed by tube thoracostomy. Patients usually present with respiratory distress, tachycardia, unilateral absence of breath sounds, hypotension, and neck vein engorgement. Although difficult to assess, these patients have tracheal deviation that is often limited to the thoracic cavity.

Not all simple pneumothoraces require drainage, as they may resolve spontaneously. Conservative management has shown a spontaneous resorption rate of 1.25% per day.46 A pneumothorax should be drained if the patient complains of dyspnea, dyspnea on exertion, pain, or if the pneumothorax is estimated to be 15% or greater.

Contraindications

There are no absolute or relative contraindications to relieving a tension pneumothorax, as it is a life-threatening emergency.

Contraindications to thoracentesis to relieve a simple pneumothorax are few. These include infection at the site of the procedure, in which case an alternate site should be selected.3 A traumatic pneumothorax or a pneumothorax associated with a hemothorax or pyothorax requires tube thoracostomy. Any pneumothorax that is expanding or expanding despite thoracentesis also requires a tube thoracostomy. Any patient on anticoagulation or with a suspected bleeding diathesis, whether known or suspected, may require reversal of the condition before the procedure.1 A patient with minimal symptoms and a small pneumothorax may be observed before deciding to evacuate the pneumothorax.

Equipment

Pneumothorax—Tension

• Alcohol swab, povidone iodine solution, or chlorhexidine solution
• 12 to 16 gauge catheter-over-the-needle, 2 in. long

Pneumothorax—Stable

• Sterile gloves and gown
• Face mask with a face shield or goggles
• Povidone iodine or chlorhexidine solution
• Sterile gauze sponge
• Sterile towels
• Sterile basin
• Syringes for anesthesia infiltration, 5 and 10 mL
• 25 gauge needle for anesthesia infiltration of the skin
• 21 or 23 gauge needle for infiltration of subcutaneous tissue, periosteum, and pleura
• 16 or 18 gauge catheter-over-the-needle
• 14 to 18 gauge catheter-through-the-needle
• Pigtail or straight catheter kit
• Three-way stopcock
• 50 mL syringe
• Intravenous extension tubing
• Heimlich valve

Ultrasound Guidance

• Ultrasound machine
• 3.5 to 5.0 MHz phased-array ultrasound probe
• Sterile ultrasound gel
• Sterile ultrasound probe cover

Commercial kits have been developed and are available to provide the equipment needed to perform a thoracentesis. These kits are disposable, single-patient use, and contain all the required equipment. They save time in that the equipment does not have to be found and set up. Disadvantages include potentially increased cost and limited equipment in the kit.18 Common kits include the Pharmaseal, distributed by Baxter (Jacksonville, TX); the Arrow Clark Thoracentesis Kit, distributed by Arrow (Reading, PA); and the Argyle Turkel Safety Thoracentesis Kit, distributed by Boston Scientific (Miami, FL).3

The TRU-CLOSE Thoracic Vent (UreSil, Skokie, IL) is an alternative device to the pigtail catheter and Heimlich valve combination. It is a one-piece unit that combines an intrapleural catheter and an external one-way antireflux valve that attaches to the chest wall by an adhesive pad. Its insertion is quicker, easier, and simpler than a traditional catheter. The low profile makes ambulation and outpatient management easier for the patient. These devices are rarely available in the Emergency Department.

Patient Preparation

Explain the procedure, its risks, and benefits to the patient and/or their representative and have a consent form signed.1 Place the patient supine on the bed. Alternatively, the patient may be supine with the head of the bed elevated to 30° (Figure 40-14). Clean any dirt or debris from the skin. Identify the anatomic landmarks required to perform the procedure. Although not required, it is recommended to place the patient on the cardiac monitor, noninvasive blood pressure cuff, pulse oximetry, and supplemental oxygen. Apply povidone iodine or chlorhexidine solution to the skin surface and allow it to dry. Apply sterile drapes around the site of the procedure. Atropine should be at the bedside. It may be administered (1.0 mg subcutaneously or intramuscularly or 0.5 mg intravenously) to patients who develop symptomatic bradycardia during the procedure. The most common approach is the second intercostal space in the midclavicular line (Figure 40-14). An alternate site is the fourth or fifth intercostal space in the midaxillary line. The Emergency Physician should wear full personal protective equipment to protect themselves from contact with the patient's blood and body fluids as well as protect the patient from infection.

Tension Pneumothorax Technique

If the patient has a tension pneumothorax, thoracentesis is both a diagnostic and therapeutic procedure. A tension pneumothorax is a true life threat. Identify the needle insertion site by palpating the second intercostal space in the midclavicular line. If a tension pneumothorax is clinically evident, ultrasound guidance is not necessary prior to needle decompression and should not delay treatment. Insert the catheter-over-the-needle over the superior border of the third rib to avoid the neurovascular bundle, which is located on the inferior border of the second rib. Advance the catheter-over-the-needle into the pleural space. If time permits, a 5 to 10 mL syringe without the plunger can be attached to the catheter-over-the-needle. The syringe barrel can be used as a handle to advance the catheter-over-the-needle.

When the pleural cavity is entered, a release of pressure and a small “pop” may be felt. Stop advancing the needle. Securely hold the needle so it does not move. Advance the catheter until the hub is against the skin. Remove the needle. If the patient has a tension pneumothorax, a continuous rush of air will be heard or felt. Needle thoracentesis for a tension pneumothorax is a temporizing measure; therefore, a tube thoracostomy should be performed immediately after this life-saving procedure. Refer to Chapter 39 for complete details regarding this procedure.

Simple Pneumothorax Techniques

A primary spontaneous pneumothorax occupying over 15% of the hemithorax is the indication for simple aspiration via a thoracentesis.3 The same sterile preparation, location of fluid, positioning, anesthesia considerations, and ultrasound-guided technique apply to the evacuation of a simple pneumothorax as to a diagnostic thoracentesis.

Spontaneous pneumothoraces used to be drained by tube thoracostomy. Simple aspiration may be just as effective as a tube thoracostomy.55–60 If a tube thoracostomy is required, a small bore straight or pigtail catheter can be just as effective to manage a spontaneous pneumothorax.61–65 While an initial study recommends using small bore tubes in patients with chest trauma, further clinical information is required before this becomes standard of care.66 The advantages of a small bore catheter include: less pain on insertion, decreased need for analgesics and sedation, and the potential to discharge the patient with outpatient management.

Catheter‐over‐the-Needle Technique

Two types of catheters can be used to perform this procedure. They are the catheter-over-the-needle and the catheter-through-the-needle (Figures 40-5 & 40-6). The catheter-over-the-needle technique is most commonly used (Figure 40-5). Make a small “nick” in the skin with a #11 surgical blade at the needle insertion site. Attach a 14 to 18 gauge catheter-over-the-needle to a 10 mL syringe as a handle. Insert the catheter-over-the-needle into the nick and advance it, reproducing the original anesthetized tract (Figure 40-5A). Apply negative pressure to the syringe as the catheter-over-the-needle is advanced. Stop advancing the catheter-over-the-needle when air is aspirated. Angle the catheter-over-the-needle superiorly. Securely hold the syringe and needle so they do not move. Advance the catheter until the hub is against the skin. Withdraw the needle and syringe as a unit while the catheter remains within the pleural cavity (Figure 40-5B). When the needle is removed, quickly cover the catheter with a gloved finger. This will prevent ambient air from entering the pleural cavity. Attach intravenous catheter extension tubing to the hub of the catheter. Place a three-way stopcock attached to a 50 mL syringe onto the extension tubing. Hold the catheter hub against the skin securely. Aspirate air into the syringe and then advance the air into the room by adjusting the three-way stopcock. Air is then withdrawn manually. This process should be continued until resistance is felt. If no resistance is felt after 4 L of aspiration, it is presumed that expansion has not occurred and a continual leak of air exists from the lung into the pleural cavity; therefore a tube thoracostomy should be performed. After no more air is aspirated, close the stopcock and secure it to the chest wall. The success rate for the aspiration of a pneumothorax is 64%.67,68

Catheter‐Through‐the-Needle Technique

The second option utilizes the catheter-through-the-needle system (Figure 40-6), which is known as the Bardig Intracath system. It is not as popular as the catheter-over-the-needle systems. Place the needle on a tuberculin syringe. Insert the needle and advance it through the anesthetized tissues (Figure 40-6A). A small “nick” in the skin with a #11 surgical blade will facilitate the needle entry. Apply negative pressure to the syringe as the needle is advanced along the anesthetized tract and into the pleural cavity (Figure 40-6A). Stop advancing the needle when air is aspirated. Securely hold the needle so it does not move. Remove the syringe and cover the needle hub with a gloved finger. This will prevent ambient air from entering the pleural cavity. Angle the needle slightly superiorly and advance the catheter through the needle (Figure 40-6B). Withdraw the needle, leaving the catheter within the pleural cavity (Figure 40-6C). Once the needle is removed, do not readvance the needle, as the catheter may shear off and fall into the pleural cavity. Place a three-way stopcock attached to a 50 mL syringe onto the hub of the catheter. Place the needle guard on the needle. Secure the catheter by taping it to the skin. Withdraw air as previously described.

Seldinger Technique

Drainage can also be accomplished using a pigtail or straight catheter and the Seldinger technique (Figure 40-15). An alternative is to use a central venous catheter if a pigtail catheter is not available.18,19 Attach a 16 gauge, 2 in catheter-over-the-needle to a 5 or 10 mL syringe. Insert the catheter, as described above, aimed superiorly. Securely hold the needle and syringe so it does not move. Advance the catheter to the hub. Remove the needle and syringe. Quickly cover the catheter hub with a gloved finger. Insert the guidewire through the catheter (Figure 40-15A). Hold the guidewire securely to prevent it from falling completely into the pleural cavity. Remove the catheter over the guidewire, leaving the guidewire in place (Figure 40-15B). Extend the skin incision with a #11 scalpel blade by 3 to 5 mm to allow the catheter to enter into the pleural space without “crumpling” (Figure 40-15C). Advance the dilator over the guidewire and into the pleural cavity to dilate the tract (Figures 40-15C & D). A gentle twisting motion of the dilator as it is advanced will aid in its insertion into the pleural cavity (Figure 40-15D). Hold the guidewire securely. Remove the dilator while leaving the guidewire in place. Insert the catheter over the guidewire and into the pleural cavity (Figure 40-15E). Remove the guidewire and attach a three-way stopcock to the catheter. Aspirate the air as described previously.

Drainage Systems

Drainage systems for a pneumothorax vary in style but function with the same “one-way valve” principle. The simplest method is a flutter valve. It is best illustrated by the following noncommercial method. Cut a premoistened finger from a sterile glove. Tie the proximal end to the thoracentesis catheter with a silk suture and cut the distal end so that it is open to the air1 (Figure 40-16). This creates a flutter valve and allows air to escape with coughing or expiration and prevents air from reentering the pleural space on inspiration.

A commercial kit often contains a Heimlich flutter valve1 (Figure 40-17). The arrow on the clear protective tube covering the Heimlich valve must point away from the patient. Suction is usually not needed. Stable patients can be sent home with this setup. This includes patients with a primary spontaneous pneumothorax and a small apical pneumothorax with initial reexpansion and good apposition of the lung with the lateral chest wall. Up to 30% of patients with a secondary pneumothorax can be treated on an ambulatory basis. Additional requirements include good residual lung function, normal oxygen saturation, and an air leak adequately treated by thoracentesis.35 A contraindication to using the flutter valve is a hemothorax. A closed underwater seal system is recommended in these cases. Refer to Chapter 39 for details regarding the use of a closed underwater seal system and the other indications for its use.

Ultrasound-Guided Technique for a Pneumothorax

The same sterile preparation applies to ultrasound evaluation of a pneumothorax as for evaluation of a pleural effusion. However, a pneumothorax may be more readily identified with the patient positioned supine rather than upright. A 3.5 to 5.0 MHz phased-array probe is recommended for ultrasound-guided examination of the pleural space.22 In general, the orientation of the probe follows the convention that the probe marker should correlate to the reference point in the left upper corner of the screen.

The key ultrasound features of a pneumothorax include: absence of inspiration–expiration related “lung slide,” loss of “comet tail” artifact, and broadening of the pleural line to a thick band.24 In the case of a unilateral pneumothorax, the hemithorax suspected of having a pneumothorax should be compared to the unaffected side, with the unaffected side showing normal “lung slide,” “comet tail” artifact, and pleural line <2 mm thick.

Assessment

Relief of a tension pneumothorax will equalize the pressure between the atmosphere and the pleural space. The patient will now have a simple pneumothorax. The vital signs should begin to normalize, the pulse oximetry improves, and the respiratory distress improves. If the patient had a tension pneumothorax, they will need a tube thoracostomy followed by a chest radiograph. The patient may begin to cough when the lung reexpands. Breath sounds should be present bilaterally upon reexpansion.

If the patient does not improve clinically after needle decompression for a tension pneumothorax, there are two possibilities. First, the pleural space may not have been entered with the needle. This occurs when the patient is obese or very muscular. The procedure may then be repeated with a longer needle. Second, the patient may not have had a tension pneumothorax. Reevaluate the patient by physical examination, bedside ultrasonography, and review the chest radiograph to determine if a tension pneumothorax is present.

Obtain a chest radiograph after the relief of a simple pneumothorax. It will allow the Emergency Physician to determine the success, or lack thereof, of the procedure. Perform a tube thoracotomy if at any point the pneumothorax is not improving with a thoracentesis or if the patient's symptoms worsen.

Aftercare

Obtain a follow-up chest radiograph upon completion of the procedure to assess for a pneumothorax. An expiratory film should be obtained, especially if the pneumothorax was small. A chest radiograph should be repeated 4 to 6 hours after the procedure to look for a delayed pneumothorax. If no pneumothorax is present and if appropriate for their clinical condition, the patient may be discharged with good instructions and close follow-up. An alternative is placement in an observation unit and discharge within 24 hours.69

The procedure site should be evaluated two to three times a day for signs of infection. These patients should be educated about the signs, symptoms, and significance of an infection. They should return to their primary physician or Emergency Department immediately if they develop fever, chills, shortness of breath, redness or pus at the puncture site, or if any concerns arise.

A patient may be a candidate for outpatient management with a Heimlich valve under the following conditions: a stable primary spontaneous pneumothorax, close apposition of the lung to the lateral chest wall with initial thoracentesis or aspiration and drainage procedures, Emergency Physician satisfaction with the position of the catheter, and an air leak that is manageable with one thoracentesis. A small study has confirmed this outpatient management, whereas many Emergency Physicians have been managing patients like this for years.70 Contraindications for outpatient management include traumatic pneumothoraces, secondary pneumothoraces, a patient with poor residual function, a large air leak requiring tube thoracostomy, a hemothorax, unacceptable residual collapse defined as poor apposition of the lateral lung to the lateral chest wall, or if the patient is not reliable.6

Instructions to the patient should include the following: clean the thoracentesis site with mild soap daily; apply a split dressing around the catheter and tape it to the skin; make sure that the tubing is taped firmly to the valve to prevent accidental dislodgment; the arrow on the valve should point away from the patient; the sound of air exiting the valve is expected; and showers are permitted but not a bath or swimming. If these patients experience shortness of breath, chest pain, or difficulty breathing, they should call 911 and immediately return to the Emergency Department. Instruct the patient on the removal of the Heimlich valve from the catheter if significant shortness of breath develops as they may have developed a tension pneumothorax. They should also be instructed on the signs of an infection at the chest wall insertion site.

The patient should follow-up daily for radiographic evaluation. Upon complete inflation of the lung, the thoracentesis catheter can be removed. The patient should be observed for 4 to 6 hours after catheter removal and a repeat chest radiograph obtained. The patient can be discharged if the lung is completely expanded. If not, a thoracostomy tube should be reinserted and the patient admitted.

Complications

Complications associated with this procedure can be numerous. Clinically, a pneumothorax can become worse. Causes include lacerating the lung with the needle, inadequate coverage of the hub of the needle or catheter with a gloved finger after entering the pleural space, and an air leak in the drainage system. It may also occur from a lung parenchymal-pleural fistula that can develop from poor lung expansion during large-volume pneumothorax drainage.71 A tension pneumothorax can occur from a lung laceration along with inadvertent plugging of the drainage system (e.g., fluid in tube, kinking). A hemothorax is possible if the lung, intercostal artery, or mammary artery is lacerated with the needle. Less common complications include cardiac or great vessel perforation due to poor positioning of the needle upon insertion. Infection occurs about 2% of the time if sterile technique is observed. Catheter shearing is possible with the catheter-through-the-needle system if the needle guard is not placed on the needle or the catheter is withdrawn through the needle. Many of these complications can be prevented by the use of proper and careful technique.

Reexpansion hypotension has been reported following rapid evacuation of persistent unilateral pneumothoraces of at least 1 week duration. The mechanism is unclear. It is associated with reexpansion pulmonary edema that precipitates intravascular volume depletion, myocardial depletion, or large volume aspiration.1 Reexpansion pulmonary edema may be precipitated by pneumothoraces over a few days duration before reexpansion or large volume aspiration.72–74

A thoracentesis can help differentiate between transudates and exudates. Together with the clinical presentation, the information can be useful in diagnosing the patient's condition. It can be lifesaving if the patient has a tension pneumothorax. It offers an alternative to tube thoracostomy for patients with stable spontaneous primary pneumothoraces. Outpatient management can be considered in some cases with the addition of a Heimlich valve. Regardless of what method is used, physicians in training should be supervised until competency with this procedure is demonstrated.