II. Describe a Step-by-Step approach/method to this problem.
- When should I do it?
- What might stop me from doing it?
- How do I learn how to do it?
- Am I allowed to do the procedure independently?
- Do I need a pre-assembled tray, and which one should I use?
- What supplies do I need if I don’t use a thoracentesis tray?
- How should I use ultrasound to guide thoracentesis?
- How should the patient be positioned and prepared?
- III. Common Pitfalls.
Thoracentesis is a percutaneous procedure that uses a needle or small catheter to remove accumulated fluid from the pleural space. Thoracentesis can either be “diagnostic” (~100 mL of fluid removed for analysis) or “therapeutic” (removal of a larger amount of fluid to relieve dyspnea). It is typically performed at the patient’s bedside and can be performed by a single operator or with an assistant.
II. Describe a Step-by-Step approach/method to this problem.
When should I do it?
Diagnostic thoracentesis is generally indicated whenever clinical exam or imaging discovers a “new” pleural effusion. The low-threshold to invasively sample pleural spaces is justified by a wide range of serious pathologies that manifest with an effusion. Therapeutic drainage (i.e. removal of larger volumes to relieve dyspnea) can be done simultaneously with the first diagnostic drainage procedure.
Effusions that do not typically warrant thoracentesis are those that are small and those with an easily identified etiology based on history (pleurisy, chronic heart failure, end-stage renal disease). Pleural effusions (infections, malignancy), which are “dangerous” etiologies, tend to enlarge over time. Thus reviewing serial imaging may help clarify the need for thoracentesis.
What might stop me from doing it?
The decision to proceed with thoracentesis should be made by weighing the benefits against the risks, as there is no absolute contraindication to thoracentesis. Clinical situations with an increased risk of complications are:
The presence of coagulopathic states, systemic anticoagulation, platelet dysfunction (pharmacologic or uremic), or thrombocytopenia: These conditions are traditionally thought to increase the risk of bleeding into the pleural space (hemothorax). Several recent studies found that pre-procedure coagulation abnormalities were not associated with bleeding complications. This suggests that avoiding intercostal vessel injury with proper technique may be more important than correcting a coagulopathic profile.
A small effusion size. Small is defined as <1 cm depth of the pleural fluid pocket on ultrasound (or a similar measure on radiographic studies). Smaller effusions increase the risk of pneumothorax due to inadvertent lung puncture.
Patients on mechanical ventilation with positive end-expiratory pressure (PEEP): If the lung is punctured by the needle on positive pressure ventilation, there is an increased risk of a persistent air leak (i.e., bronchopleural fistula) and/or tension pneumothorax.
Patients with evidence of skin or soft tissue infection overlaying the site of needle insertion: In this situation, the procedure may seed the pleural space with skin pathogens, causing a pleural infection.
Patients with severe lung disease of the contralateral lung: Patients with advanced bilateral lung disease or a single functioning lung (as in post single-lung transplant) may not tolerate even a small pneumothorax.
Patients with a long-standing loculated effusion or thickened pleura on imaging. These patients are at higher risk for a pneumothorax and/or inability to drain the effusion. Long-standing pleural inflammation (e.g., an untreated pleural infection) leads to deposition of a stiff layer of fibrotic material onto the visceral pleura, fixing the volume of the pleural cavity. When pleural fluid is aspirated from the pleural cavity via a thoracentesis needle, the lung is unable to expand to fill the pleural space and thus the pleural cavity pressure quickly falls. This very negative pleural pressure (<20 cm H2O) creates a powerful gradient for pressure to tear lung segments and enter the pleural space, resulting in a pneumothorax.
How do I learn how to do it?
Training for thoracentesis varies greatly by institution, but generally a combination of didactic, simulation, and supervised experiential training offers the optimal pathway to competence. Specific training in ultrasound-guided technique is rapidly becoming standard. If one has not had adequate training in the course of residency training, attending a CME course held by nationally-recognized professional organizations (i.e., SHM, ACP, ACEM, ATS, or CHEST) can provide additional didactic and simulation training prior to undergoing proctored procedures necessary for privileging.
Am I allowed to do the procedure independently?
For those who have completed their graduate medical education, one should consult their institution’s credentialing system to ensure appropriate privileges are granted to perform thoracentesis. For resident physicians or fellows, your training program usually has an educational pathway, typically starting with supervised thoracentesis with gradually increased autonomy as one becomes more experienced.
Do I need a pre-assembled tray, and which one should I use?
The standard tray for thoracentesis contains a drainage catheter threaded either through or over a needle as well as other components. For a therapeutic tap, it is advisable to use a pre-assembled procedure tray, as these will contain the stopcock, drainage tubing, and fluid collection bag that would be time-consuming to acquire otherwise.
More recently, pre-assembled trays using a small 6 French silicone-coated self-directing pigtail catheter threaded over a dual lumen blunt obturator have become widely available. If available, these trays are preferable to the standard thoracentesis tray because of a number of safety features. The needles in these trays have a visual color indicator at the base, where the indicator changes color once a spring-loaded core in the obturator is extended. This indicates that the needle has been advanced into a low-resistance environment, presumably the pleural space. This feature provides a number of advantages over standard trays, including (1) protection from needlestick injury (2) reduced risk of injury to free-floating atelectatic lung (3) added visual evidence of needle advancement into the pleural space. Creating a skin incision with a scalpel prior to needle insertion is required due to skin resistance to the surrounding plastic catheter’s advancement. The catheter will “accordion” unless a proper incision is made.
What supplies do I need if I don’t use a thoracentesis tray?
A small volume diagnostic tap can be performed without a kit. You will need the following supplies:
A 1.5 inch 18- or 20-gauge needle for thinner patients, or the longer 20-gauge spinal needle for more obese patients
Lidocaine solution (10 mL of 1% lidocaine is typically sufficient)
2% chlorhexidine is preferred over a povidone-iodine solution for preparing the site
Sterile drapes, gloves, mask, and cap.
A 60 mL syringe
A portable ultrasound machine
Specimen containers, depending on the testing ordered:
LDH, glucose, total protein, chylomicrons, cholesterol, adenosine deaminase 2 (red-top tube)
Cell count (purple-top tube)
Bacteriology, mycology cultures (blood culture bottles)
Cytology (black top, specimen cups, or the large 2 L plastic collection bag that is frequently provided in thoracentesis kits)
Tuberculosis testing (black top or specimen cups)
pH (blood gas syringe)
How should I use ultrasound to guide thoracentesis?
Ultrasound guidance is rapidly becoming standard-of-care with all thoracentesis, and recent guidelines strongly recommend its use in all pleural procedures. Typically, a low frequency (3.5 to 5 MHz) convex array probe is used, although a high frequency linear transducer (7.5 to 10 MHz) can be used as well. The low frequency convex array probe (i.e., the cardiac probe) is by convention held with the indicator dot directed cephalad and images are obtained in the sagittal (when imaging the posterior chest) and coronal (when imaging in the mid-axillary line) planes.
On ultrasound, the fluid pocket is seen as a hypoechoic (black) space between the chest wall and the underlying lung and visceral pleura, which is hyperechoic (
Typical low-frequency convex probe position on a patient with the resulting ultrasound view of a large simple pleural effusion. White labels indicate orientation of the ultrasound image and yellow labels identify structures. Note the green indicator dot on one side of the ultrasound probe, corresponding to the green dot in the upper left side of the ultrasound image. Thus, when the probe is held in this orientation, the left side of the ultrasound image is cephalad.
Select an entry location where the pleural fluid pocket provides the widest distance between the chest wall and the visceral pleura. Indent the skin at this location with pressure from a pen-cap or mark this site with a permanent marking pen. Once marked, the patient should remain in the same position for the duration of the procedure. Care should be taken to avoid the diaphragm (appears as a highly echogenic structure) and the underlying solid organs.
Keep in mind the anatomy is dynamic with respiration, and monitor the potential site of entry throughout the respiratory cycle. If possible, chose a site near the posterior axillary line, as angiographic studies show ectatic vessels are less likely to be encountered here than in more medial positions along with a wider intercostal space. There is also less musculature that will need to be traversed. Color Doppler ultrasound can screen for tortious intercostal vessels at a potential needle-entry site, and may reduce the risk of vessel injury. If loculations are present, sample the largest loculation and monitor pleural pressure intermittently during the drainage.
For the occasional instance when ultrasound is not available, a “blind” thoracentesis can be performed. First, make sure the effusion is non-loculated and large. Decubitus chest films may be helpful, to ensure that the effusion is mobile and moves freely with the pleural space. Select an entry site that is 1-2 interspaces inferior to the superior extent of the effusion, as determined by physical exam (dullness on percussion, decrease in tactile fremitus and/or breath sounds). Additionally, select a site that is above the ninth rib (to avoid subdiaphragmatic puncture). Rib palpation is often easiest in the line midway between the spine and posterior axillary line.
How should the patient be positioned and prepared?
Ideally, a nurse or assistant who is familiar with thoracentesis can assist with positioning and setup. Typically, the patient sits at the edge of the bed, leaning forward over a bedside table with arms and hands resting on a pillow. The patient’s arms should be at shoulder level to aid in the “bucket handle” motion of the rib spaces, which will widen the intercostal space. A footstool, if available, should be provided. The patient should be at the foot of the bed with the affected side facing the foot of the bed. This allows the operator to avoid leaning over the entire width of the bed. The space behind the patient can be used for the procedure tray, or this can be placed on a separate procedure stand. The bed should also be raised to a height comfortable to the operator. If this positioning is not possible, the patient can lie in a lateral decubitus position with the affected side facing the bed, or sitting upright as much as the hospital bed will allow.
After locating the entrance site with ultrasound and making an appropriate mark, the field should be sterilized. If chlorhexidine is used, the area should be scrubbed for at least 30 seconds, followed by 2 minutes of drying. If using povidone-iodine, three successive coats should be applied in enlarging concentric circles, with adequate time allowed between coats for drying. As some studies have shown that use of 2% chlorhexidine is more effective at preventing infectious complications of procedures than iodine solutions, we favor the use of chlorhexidine.
What are the specific procedural steps in a thoracentesis?
Preparation and time-out: Review labs and medications to assess the risk of bleeding, and review imaging studies to select an entrance location. Obtain informed consent. Gather your supplies and ultrasound, position the patient, and select your entry site. The operator should sterilize his or her hands, don a surgical gown, protective eye-wear, cap, and sterile gloves. Before anesthetizing the patient, a time-out should be performed according to local practice, ensuring verbal identification of the procedure and appropriate site and side.
Local anesthesia: Using a 25-gauge needle, a small wheal should be raised using 1% lidocaine at the marked site. Lidocaine without epinephrine suffices as this is typically not a bloody procedure. After the superficial skin is numb, swap your anesthetic needle out for the longer 18- to 22-gauge needle. Using a cycle of advance-aspirate-inject (advance needle, aspirate to assess for fluid, inject lidocaine), the needle should be advanced from the skin surface in a somewhat cephalad direction over the top of the rib inferior to the marked site. “Walking” the needle over the rib ensures proper anesthesia of the rib, as well as maintaining a needle trajectory that is appropriately distanced from the intercostal neurovascular bundle (generally running under each rib). The parietal pleura is richly innervated, so as your needle approaches the parietal pleura, liberally apply lidocaine. Typically, 7-10 mL of 1% lidocaine is sufficient for the entire procedure.
If one is performing a diagnostic tap, the needle can be advanced until pleural fluid is aspirated, after which a 60 mL syringe can be used to obtain a sample. In this method, take care to use a stopcock to avoid introducing air into the pleural space. If a therapeutic tap is being performed, note the needle depth and angle at which pleural fluid is obtained, as this is the targeted trajectory for the drainage catheter insertion.
Placement of drainage catheter: After entering the pleural space with the small gauge needle and applying lidocaine, a scalpel is used to create a small skin incision to allow entry of the larger bore catheter through the skin. Subsequently, the needle/obturator and catheter assembly should be advanced along the same trajectory taken by the anesthetic needle. The syringe attached to the assembly should be drawn back while the needle is advancing. Care should be taken to apply equal pressures with the hand at the skin surface and the hand on the syringe, so as to avoid flexing the needle-catheter assembly. See below for signs/symptoms of complications which would necessitate stopping the procedure. Pleural fluid should be aspirated at the same depth as noted during deeper injection of lidocaine; if not, repeat assessment of the fluid pocket with ultrasound should be undertaken, as the fluid pocket may have shifted. Once pleural fluid is aspirated, the needle/obturator is advanced another millimeter, after which the catheter is slowly advanced into the pleural space while the needle/obturator is kept at the same depth. Then the needle/obturator is removed slowly and remains external to the skin surface for the remainder of the procedure.
Drainage of pleural fluid and determining when to stop: The drainage tubing is attached to the stopcock, and a 60 mL syringe is attached to either the side port of the stopcock (in the case of a straight drainage catheter) or to the bidirectional end of the Y-tubing included in some trays. Fluid is then hand-aspirated using the 60 mL syringe, and then enters the 2 L collection bag via the efferent limb of the Y-tubing. The procedure should be stopped when any of the following occur:
No further fluid can be aspirated.
The patient develops persistent coughing or chest pain.
1.5-2 L of fluid has been drained.
This ~2 L upper limit on volume removal is a general guideline, rather than an inviolable limit. There are many reports of uncomplicated removal of very large pleural fluid volumes (>3-6 L), and it is clear that some patients will tolerate a very large volume removal. However, a 9,000 patient single center retrospective analysis found the removal of more than 1.5 L of pleural fluid is associated with increased risk of reexpansion pulmonary edema and pneumothorax. Additional studies found a substantial stepwise increase in complication rates for every additional 0.4 L removed above 1.8 L. In addition to the removed volume, one can monitor pleural pressure periodically with a disposable manometer or with a fluid column, which can avoid the development of excessively negative pleural pressure. This will reduce the risk of pneumothorax and reexpansion pulmonary edema, with a “stopping point” occurring when the pleural pressure falls to around -20 cm H20. Finally, because vacuum bottles apply a constant excessive negative pressure and do not allow one to “feel” when pleural pressure is becoming increasingly negative, some suggest they should not be used during thoracentesis as they may increase the risk of pneumothorax.
Needle removal: Once the desired amount of fluid is removed, the catheter can be removed. Having the patient hum while pulling the catheter makes the pleural pressure higher than atmospheric, avoiding inadvertent air entry into the pleural space as the catheter is pulled. A bandage is placed over the entry site.
Post-procedure assessment: The patient should be re-examined after the procedure to reassess the size of the pleural effusion. From a safety perspective, routine post-procedure chest radiographs are unnecessary, but are frequently obtained to assess the size of the residual pleural effusion after drainage.
III. Common Pitfalls.
I aspirate air while advancing my needle/catheter? This can be a sign of a pneumothorax. The needle should be withdrawn and a portable chest x-ray should be obtained immediately. Supplemental oxygen should be provided. Treatment of a pneumothorax is discussed in a separate entry.
I aspirate blood while advancing my needle/catheter? This can be a sign of intercostal vessel injury. The needle should be withdrawn and a portable chest x-ray should be obtained. If there is no change in the chest radiograph and the patient’s condition, the procedure can be reattempted at a site at least 1 cm distant from the original site. Of note, malignant pleural effusions are often serosanguinous. Treatment of hemothorax and pneumothorax is discussed in a separate entry.
The patient develops lightheadedness, chest/shoulder pain, or increased dyspnea/coughing while advancing the needle/obturator? This can be a sign of a vasovagal event, pneumothorax, or hemothorax. The needle should be withdrawn and a portable chest x-ray should be obtained. Reattempting the procedure is possible if the patient’s condition resolves and there is no evidence of complication.
The patient develops right or left upper quadrant pain during or after the procedure? This can be a sign of injury to the liver or spleen, respectively. The procedure should be stopped, and a CT scan of the abdomen should be performed immediately.
The patient coughs repeatedly during the procedure. In large effusions, the occasional cough commonly occurs and can be a sign that previously atelectatic lung is now re-expanded. Alternatively, the pleural drainage catheter may be irritating the now expanded lung or the patient may be developing a pneumothorax. These coughing fits typically occur after the majority of the effusion has been drained and can suggest the need to end the procedure. If the coughing is persistent or associated with pain, it is reasonable to stop the procedure and obtain a CXR to rule out a pneumothorax.
The patient develops chest pain, hypotension, or dyspnea either during fluid aspiration or afterwards? If immediate, this can be a sign of a pneumothorax. If somewhat delayed, this can be a sign of re-expansion pulmonary edema, which usually occurs within 1 hour after thoracentesis, but can occur up to 24 hours afterwards. Chest radiographs should be obtained immediately to assess for pneumothorax and reexpansion pulmonary edema, as well as any other clinically appropriate studies given the possible etiologies of these symptoms. Treatment of reexpansion pulmonary edema is discussed in a separate entry.
After a small volume of fluid is aspirated, no further fluid can be aspirated from what appears to be a large effusion? This could represent the catheter becoming “suctioned” to a pleural surface. This is more common when using vacuum bottles, and thus these should be avoided. When this occurs, some maneuvers that can re-initiate flow include pulling back slightly on the catheter, repositioning the patient, or performing the Valsalva maneuver.
What should I write in my procedure note?
Procedure notes are often written on pre-printed forms or EMR templates and should include the following elements: name of procedure; operator, and assistants (and level of training if appropriate); pre- and post-procedure diagnoses; indications for procedure; anesthetic medication and route used; type of consent obtained; use of a time-out; use of ultrasound guidance; sterile preparation of the patient; description of needle/obturator and catheter used; volume and description of fluid removed; types of laboratory analysis performed on fluid; complications (if any).
How should I bill for the procedure?
There is often confusion when deciding which CPT codes to use for thoracentesis. Code 32555 is generally used.
Can I bill if I use ultrasound guidance?
CPT code 32555 now includes the use of ultrasound and no additional code with modifier is needed.
VII. What’s the Evidence?
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