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The Sun Should Never Set on a Parapneumonic Effusion

1989; Elsevier BV; Volume: 95; Issue: 5 Linguagem: Inglês

10.1378/chest.95.5.945

1931-3543

Steven A. Sahn, Richard W. Light,

Pneumothorax, Barotrauma, Emphysema

It has been documented that pleural effusions are frequently associated with pneumonia, whether it be pneumococcal, staphylococcal, Gram-negative aerobic, or anaerobic.1Wiita RM Cartwright RR Davis JG Staphylococcal pneumonia in adults.AJR. 1961; 86: 1083-1091Google Scholar, 2Bartlett JG Finegold SM Anaerobic infections of the lung and pleural space.Am Rev Respir Dis. 1974; 110: 56-77PubMed Google Scholar, 3Taryle DA Potts DE Sahn SA The incidence and clinical correlates of parapneumonic effusions in pneumococcal pneumonia.Chest. 1978; 74: 170-173Crossref PubMed Scopus (125) Google Scholar, 4Light RW Girard WM Jenkinson SG George RB Parapneumonic effusions.Am J Med. 1980; 69: 985-986Abstract Full Text PDF Scopus (433) Google Scholar The most common cause of an empyema or complicated parapneumonic effusion today is anaerobic pulmonary infection.5Bartlett JG Gorbach SL Thadepalli H Finegold SM Bacteriology of empyema.Lancet. 1974; 1: 338-340Abstract PubMed Scopus (145) Google Scholar This is largely related to the pathogenesis of anaerobic pulmonary infection, since the disease frequently occurs in the alcoholic patient or in those with impaired consciousness and has an insidious course that does not prompt immediate medical attention. Medical consultation usually is sought seven to ten days after initial inoculation of anaerobes in the lung, when necrotization occurs in the form of necrotizing pneumonia, lung abscess, or empyema.2Bartlett JG Finegold SM Anaerobic infections of the lung and pleural space.Am Rev Respir Dis. 1974; 110: 56-77PubMed Google Scholar Due to the delay in initiation of antibiotic therapy, the patient frequently has a pleural effusion by this time. The stage of the pneumonia and of the parapneumonic effusion is critical to the outcome. If the patient can be treated early in their course with appropriate antibiotics, resolution of the pleural effusion occurs with minimal pleural sequelae. If too much time elapses, allowing the inflammatory process to proceed unimpeded in the pleural space, control of pleural sepsis and resolution of the pleural inflammation cannot occur without pleural space drainage. This often necessitates a thoracotomy or prolonged open drainage. Therefore, time is of the essence in the treatment of parapneumonic effusion. The first rule is that in patients with pneumonia, one should carefully search the chest roentgenogram for a pleural effusion, including decubitus views. If the effusion is free-flowing and greater than 1 cm from the inside of the chest wall to the pleural fluid line on the lateral decubitus view, immediate diagnostic thoracocentesis should be done. If loculated, thoracocentesis should be done under ultrasonic guidance. Following notation of the character of the fluid (including odor), the most important diagnostic tests to order are Gram stain and culture, pH, glucose, and LDH. The pleural fluid pH must be handled meticulously as an arterial pH and drawn anaerobically into a syringe rinsed with 0.2 ml of 1:1,000 heparin and placed on ice until analyzed; the pH is stable for at least 6 h using this procedure.6Light RW MacGregor MI Luchsinger Jr, WC Ball PC Diagnostic significance of pleural fluid pH and PCO2.Chest. 1973; 64: 591-596Crossref PubMed Scopus (136) Google Scholar The fluid for glucose measurement must be placed in a tube with an antiglycolytic substance to prevent in vitro glycolysis, which can occur with the numerous PMNs present in the fluid. The pH, glucose, and LDH are related, either directly (pH and glucose) or inversely (pH and LDH, glucose and LDH) in parapneumonic effusions. In uncomplicated parapneumonic effusions, the pH is >7.30, the glucose 60 > mg/dl, or the pleural fluid to serum ratio >0.5, and the LDH is <1,000 U/L, usually less than 500 U/L. In contrast, patients with complicated parapneumonic effusions (including empyema) have a pH <7.10, a glucose 1,000 U/L.4Light RW Girard WM Jenkinson SG George RB Parapneumonic effusions.Am J Med. 1980; 69: 985-986Abstract Full Text PDF Scopus (433) Google Scholar, 5Bartlett JG Gorbach SL Thadepalli H Finegold SM Bacteriology of empyema.Lancet. 1974; 1: 338-340Abstract PubMed Scopus (145) Google Scholar, 6Light RW MacGregor MI Luchsinger Jr, WC Ball PC Diagnostic significance of pleural fluid pH and PCO2.Chest. 1973; 64: 591-596Crossref PubMed Scopus (136) Google Scholar, 7Potts DE Levin DC Sahn SA Pleural fluid pH in parapneumonic effusions.Chest. 1976; 70: 328-331Crossref PubMed Scopus (119) Google Scholar, 8Potts DE Taryle DA Sahn SA The glucose-pH relationship in parapneumonic effusions.Arch Intern Med. 1978; 138: 1378-1380Crossref PubMed Scopus (65) Google Scholar All three should be measured in parapneumonic effusions. If only a single measurement is performed and it is spurious, an incorrect therapeutic decision can be made. The pH is most likely to be spurious, either because room air is allowed to accumulate in the syringe causing a false elevation of pH, or the syringe remains at room temperature allowing glycolysis to occur causing the reported pH to be falsely low.9Sahn SA Reller LB Taryle DA Antony VB Good Jr, JT The contribution of leukocytes and bacteria to the low pH of empyema fluid.Am Rev Respir Dis. 1983; 128: 811-815PubMed Google Scholar The clinician also must be cautious in interpreting the pH value in the setting of acidemia. When acidemia is present, pleural fluid acidosis is defined as a pH at least 0.15 pH units lower than blood pH. The pH cutoff for chest tube insertion in acidemia is unknown, but probably is at least 0.30 units less than blood pH. If the fluid is purulent (empyema) on thoracocentesis, drainage must be instituted, either through tube thoracostomy or at thoracotomy. In nonpurulent fluid, the Gram stain results and biochemical characteristics should be used to aid in decision making. The pleural fluid should be drained if the Gram stain is positive, pleural fluid pH is <7.10, or pleural fluid glucose is <40 mg/dl. If indications for drainage are present, the procedure should be carried out immediately, as it may only take a few hours for free-flowing fluid to loculate and greatly increase the morbidity and even mortality of the patient. A free-flowing nonpurulent fluid can usually be drained adequately with a single chest tube, while the loculated pleural space commonly needs to be evacuated at surgery. If the patient has a free-flowing, nonpurulent pleural fluid with borderline biochemical parameters (a pH between 7.29 and 7.10, glucose between 40 and 60 mg/dl, and an LDH <1,000 U/L), appropriate antibiotic treatment should be started and the patient observed over the next six to 12 h. At that time, thoracocentesis should be repeated. If the pleural fluid measurements are stable or improving, continued observation with antibiotic therapy is warranted; if there is a worsening of these measurements, chest tube drainage is generally necessary for resolution. We tend to be aggressive with our recommendation for tube drainage, since we would rather have a few too many chest tubes placed than obtain a result requiring thoracotomy, empyectomy, and decortication if the drainage had not been done or was delayed. We think that the adage "the sun should never set on a pleural effusion" should be modified to read "the sun should never set on a parapneumonic effusion," because timing is most critical in appropriate management. A final note: the value of pleural fluid in aiding the decision on pleural space drainage is only relevant to parapneumonic effusions and should not be used as a criterion for drainage in other causes of low pH effusions such as rheumatoid pleurisy, tuberculosis, malignancy, or lupus pleuritis.10Kaplan Jr, JT Good RL Maulitz RM Taryle DA Sahn SA The diagnostic value of pleural fluid pH.Chest. 1980; 78: 55-59Crossref Scopus (89) Google Scholar