Management of Parapneumonic Effusions

Annotation for Point C

A pleural pH less than 7.2 (or glucose G60 mg/dL) is diagnostic of infection and warrants prompt tube thoracostomy. The optimal size of the chest tube remains debated, 3,35,36 but a guide wire inserted 18F seems effective in removing this hypercoaguable fluid. This is a grade B recommendation. These smaller chest tubes are associated with less chest wall pain than blunt dissection- inserted tubes, without compromise in clinical outcome. The position of the chest tube, however, is important.35 The tube should be placed in the posterior (dependent) pleural space and not within a pulmonary fissure. We have observed that the typical ‘‘trauma’’ chest tube37 introduced through the fifth intercostal space (ICS), at the mid-clavicular line, favors fissure placement. Consequently,we recommend ultrasonographyguided tube insertion via the sixth ICS. But this is based on our unpublished experience (level V therapeutic evidence). A Gram stain and culture of the pleural fluid should be obtained at the time of tube thoracostomy to differentiate the organism, although 20% to 40% of the time, there is no reported identifiable pathogen.38-42 More recent techniques such as countercurrent electrophoresis, latex agglutination, or bacterial DNA detection by polymerase chain reaction should improve pathogen identification.9 This is currently a grade C recommendation. The most comprehensive prospective analysis of bacteria in empyema is the United Kingdom Multicenter Intrapleural Sepsis Trial (MIST I).40,41 In empyema associated with community-acquired pneumonia, the most common pathogen (Table 1) was Streptococcus milleri (32%), whereas if hospital acquired, it was methicillin-resistant Staphylococcus aureus (28%). Patient characteristics, including diabetes, alcoholism, age older than 60 years, and trauma are associated with more anaerobic and resistant gram-positive organisms.37,38 Hospital-acquired empyema is reported to have a fourfold greater risk of death compared with community acquired.39 The relatively poor outcome with S. milleri is postulated because of the frequent presence of anaerobes.43,44  Thus, presumptive antibiotics should be based on the type of pneumonia (community vs. hospital acquired), the pathogens identified in the antecedent pneumonia, and patient comorbidities.38-44 Of note, although most antibiotics penetrate the pleura well, aminoglycosides may be inactivated at a lower pH.45