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 But this is based on our unpublished experience (level V therapeutic evidence).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