INTRODUCTION AND EPIDEMIOLOGY
Empyema is a pleural space infection with pus, a positive Gram stain or culture, or parapneumonic effusions without pleural fluid sampling. Causes of empyema include pulmonary infections, most commonly bacterial pneumonia (56%), complications of chest surgery (22%), trauma (4%), esophageal perforation (4%), complications of chest tube/thoracentesis (4%), an extension from a subdiaphramatic infection (3%), and other causes (7%), such as osteomyelitis or other near pleural infections or a hemothorax, chylothorax, or hydrothorax that becomes infected.1
Predisposing factors for empyema include aspiration pneumonia (and the conditions causing this event, notably neurologic disease altering swallowing), respiratory disease impairing ciliary function, immunocompromise, malignancy, and alcoholism. The common organisms in empyema stratified by associated pathology are listed in Table 66-1.1
TABLE 66-1Common Organisms in Empyema and Associated Pathology ||Download (.pdf) TABLE 66-1 Common Organisms in Empyema and Associated Pathology
|Pathology ||Organisms |
|Pneumonia || |
|Pneumonia (unimmunized with Haemophilus influenza type B vaccine) ||Haemophilus influenza |
|Lung abscess ||Mixed oropharyngeal anaerobes |
|Aspiration pneumonia ||S. aureus |
|Recent thoracotomy ||Gram-negative bacilli |
|Pneumonia in the setting of human immunodeficiency virus || |
|Chest trauma || |
|Contiguous abdominal infection || |
|Esophageal rupture ||Mixed oropharyngeal organisms |
Suspect empyema if symptoms of pneumonia (fever, cough, dyspnea, pleuritic chest pain, and malaise) do not resolve. The onset of empyema may be insidious, with patients appearing chronically ill with weight loss, anemia, and night sweats.
Physical examination findings include decreased breath sounds, dullness to percussion, decreased tactile fremitus, and on occasion a friction rub. Pain from an underlying effusion or empyema may cause splinting with respiration. If there is an underlying pulmonary infection, rales or rhonchi may be heard.
Diagnostic criteria for empyema are aspiration of grossly purulent material on thoracentesis and at least one of the following: thoracentesis fluid with a positive Gram stain or culture, pleural fluid glucose <40 milligrams/dL, pH <7.1, or lactate dehydrogenase >1000 IU/L. In countries where tuberculosis is a common cause of exudative effusions, the negative predictive value of adenosine deaminase is 99.9% and can exclude the disease.2,3,4
Empyema has three stages that impact treatment:
Exudative (may be very short, <48 hours; the free-flowing pleural effusion that is present is amenable to chest tube drainage)
Fibrinopurulent (fibrin strands form in the pleural fluid causing loculations; resolution of the empyema with single chest tube drainage is unlikely)
Organizational (takes several weeks; more extensive fibrosis; "pleural peel" restricts lung expansion)
Treat any trigger, especially pneumonia or heart failure. Nonsteroidal anti-inflammatory drugs or opioids can aid the pleuritic pain. Thoracentesis can aid in therapy in a patient ...