Empyema

This is my catch-up blog about empyema, which we discussed on Tuesday!

1) Thoracic empyema

• Defined as pus in the pleural fluid (high PMN count) and or pH  less than 7.20. Also has high LDH due to lysis of PMNs. Progression to an empyema occurs over time and patients present subacutely with a long hx of SOB, cough etc. A dense layer of fibrin can deposit on the visceral and parietal pleurae, leading loculation and worse prognosis. This anaerobic environment leads to the proliferation of anaerobes and other bacteria.
• Common symptoms include pleuritic chest pain, dyspnea and sputum production. Those with aspiration risk, underlying lung disease, diabetics and immunocompromised are at higher risk.
• Physical exam reveals dullness to percussion, decreased breath sounds, decreased fremitus and a loss of egophony.
• Common bacteriology:
• Prevalent bacteria include: Streptococcus milleri, Staphylococcus aureus, enterobacteriaceae, strep pneumonia, GAS, CNST
• Diabetics are at increased risk of Klebsiella pneumonia
• MRSA can cause a necrotizing pneumonia that leads to complicated parapneumonic effusions. 
• The lack of anaerobic bacteria in culture does not exclude the presence of anaerobes, espcially if the fluid has a putrid odor. Empiric coverage for anaerobes should be initiatied. Common bugs include Peptostreptococcus, Fusobacterium and occasionally Bacteroides fragilus
• Don't forget tuberculous empyema, characterized by large mounts of pleural PMNs. 
• Treatment:
• Antibiotics: Should target the likely underlying cause of the pneumonia. Options for empiric therapy that cover anaerobes as well as gram + and -  include clindamycin, amoxi-clav or piperacillin tazobactam and carbapenems. 
• Sterilization of the empyema should occur within at least 4-6 wks of therapy, but therapy should be continued if there are persistent symptoms or persistent effusion as seen on imaging.
• All complicated parapneumonic effusions and empyemas should be managed with complete pleural fluid drainage. This can be done with a pig-tail or tube thoracostomy (preferred for thick loculated empyema)
• Progress should be assessed by repeat CT imaging
• Chest tubes are typically left in place until the drainage rate is less than 50mL/day and empyema cavity has closed
• If Unsuccessful, thoracics may need to be involved for a VATS (video assisted thorascopic surgery) for debridement / decortication
• Fibrinolytic agents can also be used to improve drainage of loculated effusions/empyemas.