Author
Mark P. Brady, PA-C
Chief Physician Assistant
Department of Emergency Medicine
Cambridge Hospital
Cambridge Health Alliance
Cambridge, Massachusetts
Disclosure: Mark P. Brady, PA-C, has disclosed no relevant financial relationships.
Editor
Lars Grimm, MD, MHS
House Staff
Department of Internal Medicine
Duke University Medical Center
Durham, North Carolina
Disclosure: Lars Grimm, MD, MHS, has disclosed no relevant financial relationships.
Reviewer
Richard S. Krause, MD
Senior Faculty
Department of Emergency Medicine
State University of New York at Buffalo School of Medicine
Buffalo, New York
Disclosure: Richard S. Krause, MD, has disclosed no relevant financial relationships.
Thoracentesis is a procedure usually done at the bedside under local anesthesia to remove fluid from the pleural space. When fluid accumulates within the pleural cavity pleural fluid analysis can provide clinically useful information. In symptomatic patients with large pleural effusions the procedure can be both diagnostic and therapeutic. By removing excess fluid symptoms, lung function may be improved. Image on right courtesy of Wikimedia Commons.
Question: The leading cause of pleural effusions in the United States is?
a. Congestive heart failure
b. Pneumonia
c. Cancer
d. Pulmonary embolus
Answer: The estimated incidence of pleural effusion is 1 million cases per year, with most effusions caused by congestive heart failure (80% of which are bilateral effusions of equal size), followed by infections, malignancy, and pulmonary emboli.
Pleural effusions can be classified as transudates or exudates. Transudative effusions result from increased hydrostatic pressure, such as in heart failure or peritoneal dialysis, or decreased plasma oncotic pressure, such as in cirrhosis and nephrotic syndrome. Exudative effusions are the result of local destruction of tissue or inflammation from conditions such as pulmonary embolism, systemic lupus erythematosus, rheumatoid arthritis, infection, or malignancy. Two thirds of malignant pleural effusions in women are secondary to breast and gynecologic cancers. Image on right courtesy of Wikidoc.
Patients with new pleural effusions, except those clearly due to heart failure or small parapneumonic effusions should have a diagnostic thoracentesis. The diagnosis of effusion is usually made by chest x-ray. An upright chest x-ray may show loculations (yellow arrow) and air-fluid levels. A lateral decubitus chest x-ray with the affected side down is more sensitive for small effusions and may show layering (blue arrows). Layering indicates free-flowing fluid and if it is at least 1 cm thick indicates effusion > 200 ml. Failure to layer may indicate a loculated effusion. Four types of fluids can accumulate in the pleural space: blood (hemothorax), serous fluid (hydrothorax), pus (pyothorax or empyema) and chyle (chylothorax).
CT scans can aid in the diagnosis of pleural effusions. A scan may reveal cystic vs solid lesions, and peripheral lung abscesses vs loculated emypemas. CT can also helps identify necrotic areas, pleural thickening, nodules, and masses. The image shown reveals a large hydropneumothorax (Arrow A = air, B = fluid). Ultrasound (yellow arrow) can be used at the bedside before thoracentesis to assess for loculations. Ultrasound can also aid during the procedure to assess diaphragmatic excursion and guide needle placement. Background image courtesy of Wikimedia Commons.
A 78-year-old male patient with advanced emphysema and atrial fibrillation presents with worsening shortness of breath and nonproductive cough over the past week. He is oxygen dependent and takes a calcium-channel blocker and warfarin. His chest x-ray reveals a new left-sided pleural effusion. His international normalized ratio (INR) is supratherapeutic at 4.8. B-type brain natriuretic peptide (BNP) and echocardiogram are normal. His vital signs are stable except for a fever of 101.2°F and oxygen saturation of 85%. He is confused, uncooperative, and coughing.
Question: Contraindications for thoracentesis in this patient include all of the following except?
a. Coagulopathy
b. A new unilateral left-sided effusion
c. Uncooperative patient
d. Severe lung disease
Answer: b. A new unilateral left-sided effusion is an indication for a diagnostic thoracentesis.
Contraindications for thoracentesis in this patient include: confusion and inability to cooperate during procedure, severe lung disease with increased risk for pneumothorax, and coagulopathy (INR > 2) with an increased risk for bleeding.
After obtaining consent for the procedure collect equipment and preorder diagnostic laboratory studies as indicated. Most thoracentesis kits (shown) include:
• Thoracentesis catheter typically consists of an 8-French catheter over an 18-gauge, 7.5-inch needle with 3-way stopcock and a self-sealing valve;
• Two injection needles for local anesthesia (22 gauge, 1.5 inch and a 25 gauge, 1 inch);
• Lidocaine 10-mL ampule of 1% or 2% solution;
• Luer lock syringes (5, 10, and 60 ml);
• Tubing set with aspiration/discharge device;
• Chlorhexidine solution;
• Specimen cap for 60-mL syringe;
• Specimen tubes;
• Drainage bag or evacuated bottles;
• Drape and sterile towels;
• #11 blade scalpel; and
• Adhesive dressing and gauze pads.
Alert and cooperative patients may be comfortable in a seated position leaning forward (shown), resting their head and arms on a pillow placed on a table beside the bed. After positioning the patient and prior to prepping, consider ultrasonography to confirm the pleural effusion, assess its size, look for loculations, and determine the optimal puncture site. On ultrasound images, freely floating lung can be seen as wavelike undulations on the M-mode tracing (arrow). Bedside ultrasound should also be used to clearly identify the brightly echogenic diaphragm and assess diaphragmatic excursion. Use of ultrasound is associated with a lower rate of complications.
Remember to select an interspace above the respiratory path of the diaphragm. Traditionally, this is described to be between the 7th and 9th rib spaces and between the posterior axillary line and midline. This site helps avoid possible puncture of the liver, spleen, diaphragm, and descending aorta. In the midclavicular line (dotted line) percuss the fluid level and move 1-2 spaces below. Clean the site with application of a topical antiseptic such as chlorhexidine (shown) or an iodophor solution.
Place a sterile drape over the puncture site and sterile towels over work area (A). If considering mild sedation, administer intravenous medications to the patient in advance. Anesthetize the skin over the insertion site (B) with lidocaine using the 5-cc syringe with 25- or 27-gauge needle. Next anesthetize the superior surface of the rib and the pleura. The needle is always inserted over the superior margin of the rib to avoid the intercostal nerves and blood vessels that run on the inferior margin. As the needle is inserted, aspirate to check for pleural fluid. Once fluid returns, note the depth of the needle and mark it with a hemostat. This gives an approximate depth for insertion of the angiocatheter or thoracentesis needle. Remove the anesthetizing needle.
Nick the skin with the scalpel (A) to reduce skin drag as the catheter is advanced through the skin. While applying steady pressure on the patient's back with the nondominant hand (B), insert the thoracentesis needle through the anesthetized skin. Advance the needle until it encounters the superior aspect of the rib. Make sure you march over the superior margin of the rib to avoid the neurovascular bundle that runs along the inferior margin. Continue advancing the needle over the top of the rib and through the pleura, maintaining constant gentle suction on the syringe until fluid is freely aspirated. Even when the pleura is anesthetized patients may experience pain and a desire to cough when the pleura is punctured.
Prepare the flexible catheter. Most commercial devices have a marker at 5 cm (arrow). At this depth the pleural cavity is usually entered and the needle does not require further advancement, depending on body habitus. Feed the catheter over the needle introducer all the way to the hub. Attach the 3-way stopcock and tubing, and turn the stopcock to evacuate the fluid through the tubing. Aspirate the amount needed using the manual syringe pump method or a vacuum bottle. Remove the necessary amount of pleural fluid, usually at least 100 mL for diagnostic studies or more for a therapeutic effect.
The syringe pump method (shown) is more labor intensive and can cause thumb neurapraxia in the operator. Removing more than 1.5 L of fluid at any one time may increase the risk for postexpansion pulmonary edema or hypotension. A pneumothorax from laceration of the visceral pleura is more likely to occur if an effusion is completely drained. After draining the fluid turn the stopcock off to prevent air from entering the pleural space. Have the patient take a deep breath, hum aloud, and gently remove the catheter. Humming increases intrathoracic pressure and decreases the chance of pneumothorax. Next, cover the insertion site with a sterile occlusive dressing. Finally, obtain an upright chest x-ray to evaluate the fluid level and to rule out iatrogenic pneumothorax.
Complications from thoracentesis include iatrogenic pneumothorax (arrows), hemothorax, re-expansion pulmonary edema (which can occur when large amounts of fluid are removed), infection, hypotension and hepatic or splenic puncture, diaphragmatic injury, empyema, vasovagal episode, subcutaneous emphysema, air embolism, and pulmonary laceration.
What tests to consider?
Serum: LDH and total protein
Pleural fluid: Total protein, LDH, glucose, cell count and differential, pH (on ice), Gram stain (shown), culture and sensitivity, fungal stain and culture, acid-fast bacillus (AFB), amylase level if esophageal perforation or pancreatitis is suspected, cytology if malignancy is suspected.
Image (A) shows a Gram stain of mixed Staphylococcus aureus (Gram-positive cocci) and Escherichia coli (Gram-negative bacilli).
Image (B) shows a micrograph of a pleural fluid cytopathology specimen showing malignant mesothelioma, one cause of pleural effusion. Images courtesy of Wikimedia Commons.
A transudate has a low white blood cell (WBC) count, a low LDH, and low protein level. An exudate will have a high WBC count, high LDH, a high protein level, and bacteria or other infectious organisms. Exudates related to pulmonary emboli will have a low WBC count and large numbers of red blood cells. Parapneumonic effusions with fluid pH less than 7.30 with a normal arterial blood pH level are caused by the same diagnoses as listed above for low pleural fluid glucose. Parapneumonic effusions with fluid pH less than 7.1-7.2 need urgent drainage of the effusion. Parapneumonic effusions with fluid pH more than 7.3 suggest that the effusions may be managed with systemic antibiotics alone. In malignant effusions, pleural fluid pH less than 7.3 has been associated in some reports with more extensive pleural involvement, higher yield on cytology and shorter survival times.
A 62-year-old male patient presents to the emergency department with severe dyspnea and right-sided chest pain worsening over the past 2 weeks. His chest x-ray (A) reveals a massive right pleural effusion with a shift of the mediastinum towards the left. A thoracentesis is performed. Serum and pleural fluid are sent for laboratory analysis revealing a serum LDH = 200 IU/L and protein = 5.6 g/dL, while pleural LDH = 150, protein = 3.5 g/dL, WBC = 500, pH = 7.35, and glucose = 85 mg/dL.
Question: Is this pleural fluid analysis consistent with a transudate or an exudate?
Answer: Exudate.
Light's criteria for exudates: Fluid is an exudate if it meets 1 of 3 criteria:
1. Pleural fluid LDH/serum LDH > 0.6;
2. Pleural fluid protein/serum protein > 0.5; and
3. Pleural fluid LDH > upper limit of normal serum LDH.
If all 3 are negative, fluid is a transudate.
Image B. is a repeat chest x-ray of image A, revealing a right pleural effusion after partial drainage showing decrease in shift of mediastinum towards left.
Purulent fluid indicates an empyema (arrow). A putrid odor suggests an anaerobic empyema. Milky fluid suggests a chylothorax, often resulting from lymphatic obstruction by malignancy or thoracic duct injury by trauma or surgery. Grossly bloody fluid may result from trauma, malignancy, postpericardiotomy syndrome, and asbestosis-related effusion. A pleural fluid hematocrit level of more than 50% of the peripheral hematocrit level defines a hemothorax, which often requires tube thoracostomy.
Most tuberculous pleural effusions probably result from a hypersensitivity reaction to the Mycobacterium rather than from microbial invasion of the pleura. Acid-fast bacillus stains of pleural fluid are rarely diagnostic (< 10% of cases) and pleural fluid cultures grow Mycobacterium tuberculosis in less than 65% of cases.
In contrast, the combination of histology and culture of pleural tissue obtained by pleural biopsy increases the diagnostic yield to 90%. CT scan (shown) in a young patient demonstrates consolidation in the right upper lobe, ground-glass opacities in the right lower lobe, and a pleural effusion on the right side. This patient has extensive tuberculous pneumonia and is immunocompromised.
The clinical importance of pleural effusions ranges from incidental manifestations of cardiopulmonary diseases to symptomatic inflammatory or malignant diseases requiring urgent evaluation and treatment. Diagnostic and therapeutic thoracentesis is an important procedural skill for emergency physicians, hospitalists, and critical care physicians. With proper training on both the procedure itself and the use of bedside ultrasonography, providers can safely and successfully perform this core clinical skill.
Author
Mark P. Brady, PA-C
Chief Physician Assistant
Department of Emergency Medicine
Cambridge Hospital
Cambridge Health Alliance
Cambridge, Massachusetts
Disclosure: Mark P. Brady, PA-C, has disclosed no relevant financial relationships.
Editor
Lars Grimm, MD, MHS
House Staff
Department of Internal Medicine
Duke University Medical Center
Durham, North Carolina
Disclosure: Lars Grimm, MD, MHS, has disclosed no relevant financial relationships.
Reviewer
Richard S. Krause, MD
Senior Faculty
Department of Emergency Medicine
State University of New York at Buffalo School of Medicine
Buffalo, New York
Disclosure: Richard S. Krause, MD, has disclosed no relevant financial relationships.
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