Studies have shown that critical care, internal medicine and emergency medicine physicians are capable of using this modality to diagnose and treat patients with symptomatic pleural effusions with few complications while improving patient outcomes^1,11,12.

Indications

Thoracentesis is indicated for patients who present to the emergency department with dyspnea due to large, non-traumatic pleural effusions that require symptomatic relief. It is also indicated for patients with pleural effusions of any size that may require diagnostic analysis of the pleural fluid, such as when the etiology of the effusion is unclear or the condition has not responded to medical therapy as expected.

Effusions can be categorized as transudative or exudative. The most common reason for transudative effusion is heart failure, followed by liver cirrhosis and nephrotic syndrome. Exudative effusions result from increased capillary permeability and consequent movement of intravascular constituents into the pleural space. Usually this is due to an infectious or inflammatory cause such as pneumonia, malignancy, empyema, or other infections.

Relative contraindications include volumes of fluid insufficient to collect, usually < 1 cm thick on a lateral decubitus chest X-ray; bleeding diathesis and systemic anticoagulation; and cellulitis over the proposed puncture site.

Performing the Study

After informed consent, prepare the site and use standard sterile technique. Given that this procedure may be uncomfortable, consider adding anxiolysis to local anesthesia. If the patient requires mild sedation, this should be done before the procedure. As with all procedures, proper positioning is the key to success. – Thoracentesis can be performed while the patient is either sitting upright or leaning over a Mayo stand or with the patient supine.

[sidebarbar]

Figure 1. Pleural fluid, which is anechoic on ultrasound, provides great contrast between the pleural and the hyperechoic air-filled lung and other structures such as the liver, diaphragm, kidney and spleen.

[/sidebarbar]

Chest ultrasonography uses ultrasound waves reflected from media in the thoracic cavity, limiting the acoustic window to the intercostal space^6,13. As such, pleural fluid, which is anechoic on ultrasound, provides great contrast between the pleura and the hyperechoic, air-filled lung and other structures such as the liver, diaphragm, kidney and spleen (Figure 1)⁶.

Examination of the pleural space can be done with a low-frequency curvilinear or convex array 5-1 Megahertz (MHz) probe or a high-frequency linear 12-6 MHz transducer¹⁴. High frequency probes offer high resolution but at the cost of decreased depth; in patients who have larger amounts of fluid that are deeper within the pleural cavity, a low frequency convex array probe may be a better option.