Pleural effusion and thoracentesis (pleural fluid aspiration)
A pleural effusion ( definition and pathophysiology)
A pleural effusion is an excessive accumulation of fluid in the pleural space. Normally, the pleural space contains only a minimalamount of fluid that is not radiographically apparent. Thus, from a practical point of view, a pleural effusion is present when fluid in the pleural space is visible on a chest radiograph. A pleural effusion is a condition that needs diagnostic evaluation, since it may be related to disorders of the lung or pleura, or to a systemic disorder.
The visceral and parietal pleural membranes form the borders of the pleural space within the thoracic cavity. Normally, this is only a potential space, since only a small physiologic amount of pleural fluid (0.1 mL/ kg) is contained within the pleural space. Oncotic and hydrostatic pressures regulate fluid movement between the pleura. Abnormally high capillary and interstitial hydrostatic pressures (as in heart failure, or constrictive pericarditis) or an abnormally decreased capillary oncotic pressure (e.g., in nephrotic syndrome or cirrhosis) can cause an accumulation of pleural fluid (transudate, see below). Inflammatory and malignant processes can increase local capillary and pleural membrane permeability or cause lymphatic blockage. This will lead to the accumulation of exudative pleural fluid (i.e., fluid with a higher concentration protein and lactate dehydrogenase-LDH). In some conditions, diaphragmatic irritation can allow fluid from below the diaphragm to enter the pleural space (acute pancreatitis, subdiaphragmatic abscess).
Causes of a pleural effusion
Intrathoracic Causes:Pulmonary infection (parapneumonic effusion due to pneumonia, empyema, tuberculosis),
Cardiovascular causes, such as congestive heart failure, constrictive pericarditis, aortic dissection, traumatic vascular disruption, superior vena cava obstruction
Malignancy (eg lung cancer, mesothelioma, or a metastasis of a distal malignancy) Pulmonary embolism,
Subdiaphragmatic disorders (subphrenic abscess, pancreatitis etc.)
Esophageal perforation,
Sarcoidosis.
Note that of the above intrathoracic causes, the five most common are pulmonary infections, congestive heart failure (due to systolic or diastolic left ventricular dysfunction), malignant neoplasms, chest trauma and pulmonary embolism.
Systemic Causes:
Collagen vascular disease (particularly systemic lupus erythematosus (SLE) and rheumatoid arthritis)Post pericardiectomy (after heart surgery) and post myocardial infarction syndromes
Nephrotic syndrome,
Liver cirrhosis,
Pancreatitis
Myxedema,
Severe malnutrition.
Note that nephrotic syndrome, cirrhosis, and severe malnutrition are conditions that cause hypoproteinemia (reduced protein concentrations in the blood) which in turn causes the development of a pleural effusion (transudate) due to a reduced intravascular osmotic pressure.
Symptoms
Patients commonly present with dyspnea, initially on exertion, cough, and pleuritic chest pain (pain on inspiration and coughing). In many cases the patient is asymptomatic.Physical examination findings of a pleural effusion
Auscultation reveals decreased breath sounds over the site of the effusion and chest percussion reveals an area of dullness. A pleural effusion can be detected clinically (by the physical examination) when ≥500 mL of pleural fluid is present.
On the erect posteroanterior (PA) chest X-ray, pleural fluid appears as a homogeneous curved shadow at the lung base, blunting the costophrenic angle and ascending towards the axilla. The quantity of pleural fluid required in order for it to be detectable on a PA chest X-ray is at least 200 mL.
Localized effusions may occur as a result of previous scarring or adhesions in the pleural space When pleural fluid is localized below the lower lobe (subpulmonary effusion) it can simulate an elevated hemidiaphragm.
When pleural fluid is localized within the oblique fissure of a lung it appears radiologically as a rounded opacity that may be mistaken for a tumor ("pseudotumor").
Ultrasound is an excellent diagnostic test for the identification of a pleural effusion. It is also used to direct the aspiration of a pleural effusion ( both to mark the puncture site for thoracentesis and also to guide the procedure). An ultrasonic transducer with a frequency of 3.5- 5 MHz can identify reliably most pleural effusions. |The normal lung will typically appear on ultrasound as a hazy gray area, often with some reverberation artifacts. Τhe pleura appears as a brightly echogenic (white) line deep to the rib shadows. A-lines, a series of horizontal lines, parallel and deep to the pleura are also seen in many cases. These are artifacts produced by ultrasound reverberation and can be seen in a normal lung.
Pleural fluid, when present, will be identified as an anechoic (black) area of varying size in the most dependent area of the thorax, typically in the recesses above the diaphragm. The pleural fluid will be always hypoechoic (black), but depending on its consistency it may have a heterogeneous appearance with gray areas, representing more solid components (such as clotted blood).
The diaphragm is a useful anatomical landmark. On ultrasound it appears as a hyperechoic (white) line arcing over the liver on the right side or over the left kidney on the left side.
A woman, 75 years old, non-smoker with a history of hypertension, diabetes type II, permanent atrial fibrillation and moderate mitral regurgitation, complaining of effort dyspnea which has become worse in the last 2 months. She had no fever, no cough and no chest pain, the heart rate was 90 beats per minute (BPM) in atrial fibrillation and blood pressure was 165/80 mmHg. The basic blood tests were normal (normal complete blood count, normal erythrocyte sedimentation rate-ESR, normal CRP, normal routine biochemistry, except from glucose 130 mg/dl ). Echocardiography showed normal ventricular systolic function (of both ventricles), dilated atria, moderate calcification of the mitral annulus, moderate mitral regurgitation and reduced early diastolic velocity E' of the septal and lateral mitral annulus (with puse wave tissue Doppler) The latter is an indication of left ventricular (LV) diastolic dysfunction. What are the findings on the X-ray and the chest ultrasound (a frontal-longitudinal plane at the lower left hemithorax), which are the structures 1-5 on the ultrasound image, and which is the proposed initial treatment ? (A video of his chest ultrasound is also provided)
The chest X-ray shows a left pleural effusion ( it seems that also a small right pleural effusion is present, since there is also a mild blunting of the right costophrenic angle). The cardiac silhouette is enlarged (in this case due to the biatrial enlargement). The mediastinum and the trachea show a deviation towards the right side (because of the pleural fluid on the left side). The lungs have mildly dilated hilar vessels and increased vascular markings. The chest ultrasound image shows: 1 the diaphragm 2. a pleural effusion (hypoechoic space), 3 the visceral pleura, 4 a part of the basal portion of the lung, compressed by the fluid.
Let us take into account the dilated atria, the signs of mild congestion in the lungs (increased vessel markings), the tissue Doppler findings and the dilated left atrium (indications of LV diastolic dysfunction), and the history of hypertension, permanent atrial fibrillation and diabetes in conjuction with the patient's age (conditions known to cause LV diastolic dysfunction) as well as the absence of symptoms and laboratory findings, that would suggest another cause. These clues indicate that the most probable diagnosis is that the patient's effort dyspnea, as well as the pleural effusion is a consequence of heart failure due to left ventricular diastolic dysfunction (heart failure with preserved ejection fraction). This would respond to a treatment with diuretics. The patient was treated with salt restriction, furosemide (loop diuretic), a beta-blocker to control the heart rate at about 70-75 BPM and an ACE-inhibitor. The effort dyspnea and the pleural effusion were markedly reduced with the above treatment , so a diagnostic thoracentesis was not performed in this case.
To treat a pleural effusion appropriately, it is important to determine its etiology. However, in some cases, the etiology of pleural effusion remains unclear and this is not uncommon (in nearly 20% of cases). In some cases,when the etiologic diagnosis has not been established by aspiration and laboratory examination of the pleural fluid, pleural biopsy may be necessary.The treatment of a pleural effusion is usually targeted to the underlying condition (e.g. congestive cardiac failure or malignancy). Treatment of the underlying cause (e. g. heart failure, pneumonia, pulmonary embolism or subphrenic abscess)Chest x-ray findings of a pleural effusion
Localized effusions may occur as a result of previous scarring or adhesions in the pleural space When pleural fluid is localized below the lower lobe (subpulmonary effusion) it can simulate an elevated hemidiaphragm.
When pleural fluid is localized within the oblique fissure of a lung it appears radiologically as a rounded opacity that may be mistaken for a tumor ("pseudotumor").
Lung ultrasound for the identification of a pleural effusion
Pleural fluid, when present, will be identified as an anechoic (black) area of varying size in the most dependent area of the thorax, typically in the recesses above the diaphragm. The pleural fluid will be always hypoechoic (black), but depending on its consistency it may have a heterogeneous appearance with gray areas, representing more solid components (such as clotted blood).
The diaphragm is a useful anatomical landmark. On ultrasound it appears as a hyperechoic (white) line arcing over the liver on the right side or over the left kidney on the left side.
A woman, 75 years old, non-smoker with a history of hypertension, diabetes type II, permanent atrial fibrillation and moderate mitral regurgitation, complaining of effort dyspnea which has become worse in the last 2 months. She had no fever, no cough and no chest pain, the heart rate was 90 beats per minute (BPM) in atrial fibrillation and blood pressure was 165/80 mmHg. The basic blood tests were normal (normal complete blood count, normal erythrocyte sedimentation rate-ESR, normal CRP, normal routine biochemistry, except from glucose 130 mg/dl ). Echocardiography showed normal ventricular systolic function (of both ventricles), dilated atria, moderate calcification of the mitral annulus, moderate mitral regurgitation and reduced early diastolic velocity E' of the septal and lateral mitral annulus (with puse wave tissue Doppler) The latter is an indication of left ventricular (LV) diastolic dysfunction. What are the findings on the X-ray and the chest ultrasound (a frontal-longitudinal plane at the lower left hemithorax), which are the structures 1-5 on the ultrasound image, and which is the proposed initial treatment ? (A video of his chest ultrasound is also provided)
The chest X-ray shows a left pleural effusion ( it seems that also a small right pleural effusion is present, since there is also a mild blunting of the right costophrenic angle). The cardiac silhouette is enlarged (in this case due to the biatrial enlargement). The mediastinum and the trachea show a deviation towards the right side (because of the pleural fluid on the left side). The lungs have mildly dilated hilar vessels and increased vascular markings. The chest ultrasound image shows: 1 the diaphragm 2. a pleural effusion (hypoechoic space), 3 the visceral pleura, 4 a part of the basal portion of the lung, compressed by the fluid.
Let us take into account the dilated atria, the signs of mild congestion in the lungs (increased vessel markings), the tissue Doppler findings and the dilated left atrium (indications of LV diastolic dysfunction), and the history of hypertension, permanent atrial fibrillation and diabetes in conjuction with the patient's age (conditions known to cause LV diastolic dysfunction) as well as the absence of symptoms and laboratory findings, that would suggest another cause. These clues indicate that the most probable diagnosis is that the patient's effort dyspnea, as well as the pleural effusion is a consequence of heart failure due to left ventricular diastolic dysfunction (heart failure with preserved ejection fraction). This would respond to a treatment with diuretics. The patient was treated with salt restriction, furosemide (loop diuretic), a beta-blocker to control the heart rate at about 70-75 BPM and an ACE-inhibitor. The effort dyspnea and the pleural effusion were markedly reduced with the above treatment , so a diagnostic thoracentesis was not performed in this case.
Diagnostic laboratory tests of pleural fluid
Pleural fluid should be sent for cell count and differential, protein, glucose, pH determination, lactate dehydrogenase (LDH), cytology, Gram staining and bacterial culture. Amylase is ordered if there is a clinical suspicion of pancreatitis or esophageal rupture. When the pleural fluid is serosanguineous or bloody, it is useful to order a pleural fluid hematocrit.
Pleural fluid is classified as an exudate or a transudate. An exudate is characterized by a higher protein content and LDH concentration and higher specific gravity than a transudate. Inflammatory, infectious and malignant causes of a pleural effusion (e.g. SLE, rheumatoid arthritis, pneumonia, tuberculosis, adenocarcinoma of the lung, pleural metastasis, post-pericardiectomy syndrome, post-myocardial infarction syndrome, acute pancreatitis, mesothelioma), as well as pulmonary infarcts (pulmonary embolism), result in the development of an exudate. Causes of a transudate include congestive heart failure, constrictive pericarditis, hypothyroidism and conditions resulting in a low level of albumin, such as nephrotic syndrome, cirrhosis, and severe malnutrition. Transudates can be bilateral but they are often larger on the right side. A rare cause of a pleural transudate is Meigs syndrome, i.e. an ovarian tumor producing a right-sided pleural effusion.
How to distinguish an exudate from a transudate
The ratio of pleural fluid protein : serum protein, in a transudate is <0.5 and in an exudate >0.5.
A transudate has a protein concentration< 3 g/dL, whereas an exudate >3 g/dL
A transudate has a protein concentration< 3 g/dL, whereas an exudate >3 g/dL
A transudate has a ratio of pleural fluid LDH : serum LDH <0.6 and LDH level <200 IU/mL, whereas in an exudate these measurements exceed the above cutoff values.
For the specific gravity of the fluid the cutoff value is 1.016, with lower values suggesting a transudate and higher values an exudate.
Currently, Light's criteria are used to distinguish a pleural exudate from a transudate. An exudate is likely if one or more of the following criteria are met:
• Pleural fluid protein : serum protein ratio > 0.5
• Pleural fluid LDH : serum LDH ratio > 0.6
• Pleural fluid LDH > two-thirds of the upper limit of normal
serum LDH
In pleural fluid due to a pulmonary infarct, predominant cells are usually red blood cells and eosinophils.
Pleural fluid pH <7.30 may indicate a malignant effusion, connective tissue disease, or esophageal perforation.
• Pleural fluid protein : serum protein ratio > 0.5
• Pleural fluid LDH : serum LDH ratio > 0.6
• Pleural fluid LDH > two-thirds of the upper limit of normal
serum LDH
Other tests
The cell count in the pleural fluid also provides some diagnostic clues: Predominance of neutrophils tends to indicate an acute process, such as a parapneumonic effusion (a pleural effusion that accompanies bacterial pneumonia) or acute pulmonary embolism. Lymphocyte predominance is usually present in longstanding effusions (malignancy, tuberculosis) and autoimmune rheumatic disease (such as SLE, rheumatoid arthritis, although in the latter case rarely there is a predominance of polymorphonuclear cells).In pleural fluid due to a pulmonary infarct, predominant cells are usually red blood cells and eosinophils.
Pleural fluid pH <7.30 may indicate a malignant effusion, connective tissue disease, or esophageal perforation.
Further tests may be needed, according to the clinical suspicion. For example, when tuberculosis is suspected acid-fast bacillus testing (including adenosine deaminase) is indicated. An elevated amylase level in the pleural fluid suggests pancreatitis or esophageal perforation.
Measurement of NT-ProBNP (N-terminal pro-brain natriuretic peptide level) in the blood is useful when the pleural fluid is classified as an exudate by Light's criteria, although there is a clinical suspicion of heart failure. Elevated blood levels of NT-ProBNP will suggest heart failure.
Treatment
will often be followed by resolution of the effusion. In patients who have symptoms caused by large pleural effusions, therapeutic aspiration of the pleural fluid (thoracentesis) is indicated.
If the fluid is purulent (empyema) complete drainage is mandatory.
A male patient 79years old, ex-smoker, presenting with worsening dyspnea for 2 weeks. He also complained of a mild dry cough. He had no fever and no chest pain. This is his chest X-ray. What additional information does it provide about the patient's history, what is the cause of his dyspnea and what is the proposed initial management?
This patient apparently has had previous heart surgery, since the surgical clips at the sternum are depicted on his chest X-ray. There is a large homogeneous opacity of the left hemithorax covering most of the left lung with a meniscus sign, suggestive of a massive left pleural effusion. The pleural effusion was also confirmed by ultrasonography. Thoracentesis was performed in order to remove a large amount of fluid with a purpose to treat his dyspnea and also to obtain samples of the pleural fluid for laboratory testing. After the therapeutic thoracentesis, dyspnea subsided. The fluid was found to be an exudate and cytology showed malignant cells. The postprocedural chest X-Ray and chest CT scan did not show a lung tumor. Consultation with an oncologist and further testing ( abdominal CT scan, blood tests, etc) was undertaken to determine the etiology of this malignant pleural effusion, but this will not be analyzed further, because it is beyond the scope of this chapter.
Thoracentesis (pleural fluid aspiration)
Indications
Thoracentesis is the aspiration of fluid from the pleural space for diagnostic examination of pleural fluid if the cause is unknown, as well as for therapeutic reasons when a large pleural effusion causes dyspnea (shortness of breath). Thoracentesis is a word derived from the Greek words thorakas (chest) and kentesis (to pierce). A diagnostic thoracentesis is indicated when there is no clear diagnostic explanation for a pleural effusion. The first step in laboratory testing of pleural fluid is to distinguish a transudate from an exudate.Note: There are cases, where the diagnosis is already clear and thoracentesis is not needed: In patients with suspected transudative bilateral effusions, thoracentesis should not be performed unless atypical features are present (e.g., fever, pleuritic chest pain, effusions of disparate size) or the effusion does not respond to appropriate treatment.
Contraindications of thoracentesis
A bleeding disorder or patient on anticoagulation (INR > 1.8 or PTT >1.5–2 x upper limit of normal/ or thrombocytopenia with platelets < 50,000 per microliter (μL) of blood.Infected skin: Thoracentesis must not be performed through an infected area of skin.
A pleural effusion known to be loculated.
Small pleural effusion (≤ 1 cm on lateral decubitus chest X-ray)
Mechanical ventilation
Equipment for thoracentesis
Antiseptic solution (usually chlorhexidine solution or povidone-iodine Chlorhexidine is generally preferred for preparing the skin than povidone-iodine solution because it dries faster and is more effective )Sterile gloves
Sterile drapes
Lidocaine 1% local anesthetic, syringe and needle
16-gauge needle, with angiocatheter when required
10-20 mL syringe
Tubing with a 3-way stopcock
Fluid collection bottles
Technique of thoracentesis
Have the patient sit erect on the edge of the bed, leaning forward with the arms on a bedside table with 1-2 pillows on it, or on a Mayo stand. Determine the level of the pleural fluid either by physical examination (absent breath sounds and dullness on percussion) or with ultrasonography.Perform sterile preparation of the back two intercostal spaces below the upper level of the effusion (but no lower than the ninth rib). In this area, palpate the superior edge of a rib in the posterior axillary line. (Note: Another possible approach used for large effusions, is to use the 8th intercostal space in the midscapular line. The midscapular line is a vertical superficial line passing through the tip of the scapula. The 8th intercostal space lies immediately below the scapular tip. Also in this case before the puncture determine the upper level of the effusion-either by physical examination or by ultrasonography).
To summarize the above instructions: The puncture site is 1-2 intercostal spaces below the highest level of effusion in the posterior axillary or midscapular line, but not below the 9th rib.
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| Axillary lines |
Häggström, Mikael (2014). Medical gallery of Mikael Häggström 2014. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.008. ISSN 2002-4436. Public Domain.
https://en.wikipedia.org/wiki/Axillary_lines#/media/File:Axillary_lines.png
Infiltrate this area with 3-5 mL of local anesthetic. The skin, subcutaneous tissue, rib periosteum, intercostal muscles, and parietal pleura of the puncture site should be well infiltrated with the topical anesthetic (lidocaine 1-2%).
For diagnostic aspiration of pleural fluid, use a 16- or 18-gauge needle attached to a syringe. For therapeutic pleural fluid aspiration, use an angiocatheter over a needle.
Insert the needle just over the superior margin of the rib (to avoid any damage to the neurovascular bundle which is located at the inferior border of each rib). With aspiration already initiated, advance the needle perpendicular to the thorax. With continuous aspiration, the needle is advanced over the superior margin of the rib until pleural fluid is obtained. At the moment pleural fluid enters the needle stop advancing the needle and keep it steady.
If thoracentesis is performed for therapeutic purpose, once fluid is aspirated, advance the angiocatheter over the needle and then withdraw the needle. Use your thumb to cover the angiocatheter hub. Instruct the patient to briefly avoid inspiration, and attach to the angiocatheter a three-way stopcock and collection tubing. Attach the collection tubing to the collection bottle. Turn the three-way stopcock so that it is open to the tubing and remove the desired amount of fluid. As much as 1,500 mL of pleural fluid can be withdrawn, but > 1,500 ml of pleural fluid should not be removed at a time. The reason is that there is a small risk of causing re-expansion pulmonary edema, due to the abrupt removal of such a large quantity (> 1.5 L) of pleural fluid.
At the end of the procedure, remove the catheter or needle and apply a sterile adhesive dressing to the puncture site. After the procedure, obtain a chest radiograph.
If dyspnea develops following evacuation of a pleural effusion suspect re-expansion pulmonary edema (which may occur after the removal of a large amount of fluid), or pneumothorax (air in the pleural space, which may compress the lung).
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Bibliography and useful links
Karkhanis VS, Joshi JM. Pleural effusion: diagnosis, treatment, and management. Open Access Emergency Medicine : OAEM. 2012;4:31-52. doi:10.2147/OAEM.S29942.
LINK Pleural effusion: diagnosis, treatment, and management
Saguil A, Wyrick K, Hallgren J. Diagnostic Approach to Pleural Effusion.Am Fam Physician. 2014 Jul 15;90(2):99-104.
Villena Garrido V, Cases Viedma E, Fernández Villar A, de Pablo Gafas A, Pérez Rodríguez E, Porcel Pérez JM, Rodríguez Panadero F, Ruiz Martínez C, Salvatierra Velázquez Ángel, Valdés Cuadrado L. Recommendations of Diagnosis and Treatment of Pleural Effusion. Update. Archivos de Bronconeumología (English Edition) 2013;50(6):235-49.
LINK: emedicine/ Medscape: Thoracentesis Technique
Porcel JM , Light RW. Diagnostic Approach to Pleural Effusion in Adults Am Fam Physician. 2006 Apr 1;73(7):1211-1220.
Brogi E, Gargani L, Bignami E, Barbariol F, Marra A, Forfori F, Vetrugno L. Thoracic ultrasound for pleural effusion in the intensive care unit: a narrative review from diagnosis to treatment. Crit Care 2016;21(1).
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