Laboratory Medicine Summary
Diagnostic analysis of pleural fluid
Pleural fluid is labeled and sent for diagnostic analysis. If the effusion is small and contains a large amount of blood, the fluid should be placed in a blood tube with anticoagulant so that it does not clot. The following laboratory tests should be requested:
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pH level
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Gram stain, culture
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Blood cell count and differential
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Glucose level, protein levels, and lactic acid dehydrogenase (LDH) level
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Cytology
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Creatinine level if urinothorax is suspected (eg, after an abdominal or pelvic procedure)
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Amylase level if esophageal perforation or pancreatitis is suspected
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Triglyceride levels if chylothorax is suspected (eg, after coronary artery bypass graft [CABG], especially if the inferior mesenteric artery [IMA] was used; milky appearance is not sensitive)
Exudative pleural fluid can be distinguished from transudative pleural fluid by looking for the following characteristics (exudates have 1 or more of these characteristics, whereas transudates have none):
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Fluid/serum LDH ratio ≥0.6
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Fluid/serum protein ratio ≥0.5
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Fluid LDH level within the upper two thirds of the normal serum LDH level
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Image of a 48-year-old woman with cancer and large left pleural effusion (2.5 liters were removed). The patient was tachypneic, hypoxic, and reported pleuritic chest pain.
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Ultrasound image using curvilinear probe. Image shows chest wall and large volume of pleural fluid.
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Chest radiograph after thoracentesis of the cancer patient shown above.
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Ultrasound image in M-mode showing sinusoidal wave pattern. This is created by the lung moving within the large pleural effusion during respiration. The depth of the lung and the amount of fluid between the parietal pleura (adherent to the chest wall) and visceral pleura (adherent to lung tissue) are easily measured with ultrasonography.
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One option for proper positioning of patient. Easy access to the 7-9 rib space along the posterior axillary line.
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Application of chlorhexidine solution.
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Sterile drape with fenestration and adhesive strip placed over puncture site, with sterile towels draping a large work area.
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Administering anesthesia to the skin, subcutaneous tissue, rib periosteum, intercostal muscle, and parietal pleura.
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Advancing the device over the superior aspect of the rib.
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Nicking the skin with scalpel to reduce skin drag as the catheter is advanced through the skin.
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Feeding the catheter over the needle introducer.
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The 5-cm mark is at the level of the skin.
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The catheter is fed all the way to the hub.
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Use the manual syringe pump method or a vacuum bottle. The syringe pump method (shown here) is more labor intensive and can cause thumb neurapraxia in the operator.
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Sterile towels on the bed, creating a large sterile work space.
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Ultrasound image using the linear probe. Image demonstrates 2 ribs with their associated acoustic shadows, rib interspace, pleural fluid, and the presence of the diaphragm rising up into this rib interspace.
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Video clip of ultrasound using the linear probe. Image demonstrates 2 ribs with their associated acoustic shadows, rib interspace, pleural fluid, and the presence of the diaphragm rising up into this rib interspace.
