Empyema thoracis


 * A parapneumonic effusion is any pleural effusion that is associated with a bacterial pneumonia, lung abscess or bronchiectasis. 40% of all patients with bacterial pneumonia develop a pleural effusion, and the development of a pleural effusion increases morbidity and mortality as compared with an isolated pneumonia. .  In general parapneumonic effusions have 3 stages:
 * Exudative: Due to capillary leak, causing a sterile effusion that has a poly predominance, with normal glucose and pH. It is seen within the 1st 72, and will usually resolve with antibiotics alone.
 * Fibrinopurulent: Occurs during days 3-7. The pleural fluid becomes infected with bacteria, and the lactate dehydrogenase (LDH) rises, as the glucose and pH fall.  As the fibroblasts get busy, loculations develop which limits the extension of the empyema.
 * Organization: Further fibroblast activity produces a pleural peel leading to restrictive lung disease. Without definitive treatment, the empyema can drain externally (empyema necessitatis) or into the lung to produce a broncho-pleural fistula.
 * Approximately 20% of all parapneumonic effusions evolve into empyema. Hippocrates described empyema thoracis around 400 BC and predicted drainage of the pleural cavity as the treatment of choice.  The term empyema refers to either the presence of gross pus in the pleural space, or a positive gram stain on pleural fluid analysis.  60% of empyemas evolve from a parapneumonic effusion, 20% after thoracic surgery and 20% from thoracic trauma, esophageal perforation, thoracentesis or subdiaphragmatic infection.  The majority of patients who develop empyema have underlying disease, most frequently alcoholism (especially in patients with anaerobic infections), malignancy and diabetes.

Pathophysiology and Etiology
Before the development of antibiotics, Streptococcus pneumoniae was the most common bug found in empyemas. More recently, however, anaerobes have become the predominant organism in culture positive empyemas (and therefore careful anaerobic cultures should always be sent when working up parapneumonic effusions). Mixed aerobic and anaerobic infections are also common, and virtually any bug can cause an empyema, however different bugs are associated with different rates of empyema formation.

Diagnosis

 * Relies on the presence of pus or organisms on gram stain.

History and Symptoms
Most patients with empyema develop:
 * Fever
 * Leukocytosis
 * Chest pain
 * Anaerobic infections however, can be more indolent, with up to 70% of patients having symptoms for more than 1 week.
 * Additionally, these patients tend to have more constitutional symptoms including:
 * Sweats
 * Weight loss

Acute Pharmacotherapies

 * Obviously, appropriate antibiotics are indicated in all patients with an underlying infection. Drainage of the pleural space should be considered early, as delay of even a few days is associated with an increase in morbidity and mortality.
 * Indications for chest tube drainage include: a pH < 7.0, glucose < 40-50, gross pus, or organisms on Gram’s stain.
 * In borderline cases, reassessment with a repeat tap should be preformed in 12 – 24 hours. If the LDH is increasing, and the pH and glucose are decreasing, a chest tube should be placed immediately.
 * The chest tube should be at least a 28 F (smaller tubes become obstructed with fibrin clot), and left in place until the drainage is clear and yellow, and its volume is < 50 cc/day.
 * Patients will get better within 24 – 48 hours. If they don’t, suspect inadequate drainage due to loculations or inappropriate antibiotics.
 * Thrombolytics (mainly urokinase and streptokinase) have been used to break up loculations and assist drainage.
 * The typical streptokinase (SK) dose is 250,000 units in 30 – 100 cc normal saline solution (NS), and the typical urokinase dose in 100,000 units, also in 30 – 60 cc NS. They are instilled via the chest tube, left in place for 1-4 hours (chest tube clamped), and repeated daily as needed.
 * Two randomized studies comparing SK to chest tube drainage alone have shown an increase in the amount of drainage, however a statistical difference in the resolution of white blood cell (WBC) count and fever, the need for surgical drainage, or the duration of hospitalization has not been demonstrated.
 * More recently, however, VATS (video-assisted thoracoscopic surgery) has been compared to treatment by treatment with SK and chest tube drainage (SK-CT) in randomized trials.
 * Wait et.al. studied 20 patients and found that VATS was associated with a significantly higher primary treatment success (91% vs. 44%), lower chest tube duration (6 days vs. 10 days) and a lower number of hospital days (9 vs. 13). VATS was also associated with a non-significant trend towards lower hospital costs.
 * They felt that SK-CT only delayed, and did not prevent definitive treatment with VATS.
 * It should be noted, however, that the patients in Wait’s study had fibrinopurulent empyema, and not simple parapneumonic effusions or chronic empyema.
 * Obviously, the definitive answer is still out on the optimal management of empyema, however, the above data may indicate a more aggressive approach in these patients.

Acknowledgements
The content on this page was first contributed by: David Feller-Kopman, M.D.

List of contributors: