Thoracentesis should almost always be performed to confirm the presence of

Thoracentesis should almost always be performed to

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can be marked or thoracentesis performed in the ultrasonography suite.Thoracentesis should almost always be performed to confirm the presence offluid and to determine its characteristics. Fluid may be clear yellow (serous), milky(chylous), blood-tinged (serosanguineous), grossly bloody (sanguineous), or
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translucent or opaque and thick (purulent). Specimens should be taken forchemical, bacteriologic, and cytologic examination (the last uses tubes withheparin, 3 U/mL fluid, added). After thoracentesis, a sample of Gram-stainedpleural fluid sediment should be examined microscopically for bacteria and fungi.Cultures for anaerobes should be sent to the laboratory in special transport mediaor in a capped syringe.Exudateshave at least one of the following features: (1) pleural fluid/serumprotein ratio > 0.5, with pleural fluid protein usually > 3.0 g/dL; (2) pleuralfluid/serum LDH ratio > 0.6; and (3) pleural fluid LDH > 2/3 of the upper normallimit for serum. Transudatesmeet none of these criteria; they are usually clear andstraw-colored but may be blood-tinged, with an RBC count > 10,000/µL. WBCcount is usually < 1000/µL but is between 1,000 and 10,000/µL in about 20% oftransudates. The glucose level is similar to that in serum.Blood-tinged pleural fluid has little diagnostic significance. More than 15% ofpleural transudates and > 40% of exudates are blood-tinged with RBC countsbetween 5,000 and 100,000/µL. Only 5,000 to 10,000 RBCs/µL need be present tomake pleural fluid red, and only 1 mL of blood is needed to make 500 mL ofpleural fluid look blood-tinged. Grossly bloody fluids have > 100,000 RBCs/µL;bloody pleural fluids suggest trauma, malignancy, or pulmonary infarction. Ahematocrit of > 50% in a bloody pleural fluid indicates hemothorax.If the body's defenses do not control infection in a patient with pneumonia andparapneumonic effusion, the number of neutrophils and bacteria increases, and thefluid takes on the gross appearance of pus. The result is empyemaof the thorax(purulent exudate in the pleural space). Fluids with > 100,000 neutrophils/µL,bacteria seen on Gram stain, and pH < 7.2 may be presumed to be empyema evenif the fluid is not grossly purulent. Most empyemas are caused by anaerobicbacteria. Empyema can result from contamination of the pleural space by ruptureof a lung abscess; a bronchopleural fistula complicates the process. A
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bronchopleural fistula can result from internal drainage of an empyema. Empyemamay be a sequela of a penetrating wound, a thoracotomy, infection from a hepaticor subdiaphragmatic abscess, or a ruptured viscus (eg, esophagus).Total cell counts should be obtained routinely for clear or turbid fluids. Apredominance of polymorphonuclear leukocytes (PMNs) suggests an underlyingpneumonia and a parapneumonic effusion that is usually sterile even in bacterialpneumonia. In the early stages of bacterial infection, fluid is not visibly purulent,many PMNs are present, and bacteria may be seen in a Gram stain. The presenceof many small mature lymphocytes, particularly with few mesothelial cells,strongly suggests TB. In pulmonary infarction, there is usually a mixture oflymphocytes, PMNs, and mesothelial cells; RBCs may be numerous. Eosinophils
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  • Spring '17
  • johan
  • Pneumothorax, Pleural cavity, Pleural effusion, pleural fluid, pleural disease, Pluritis

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