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Complications

General complications

• Since most patients hospitalized with pneumonia are elderly and have multiple comorbid conditions, complications during the hospital stay are not uncommon.
• The most common complications are:
  • Respiratory failure
  • Congestive heart failure
  • Shock
  • Atrial dysrhythmias
  • Myocardial infarction
  • Gastrointestinal bleeding
  • Renal insufficiency
• Only ~30% of patients hospitalized for the treatment of pneumonia have no complications.
• The major systemic complication is bacteremia.
  • Can lead to metastatic infection, including septic arthritis or meningitis
    

Complicated pleural effusion

• Pleural effusion is seen in ~40% of patients hospitalized for CAP.
• All patients with a pleural effusion should have a lateral decubitus chest radiograph with the affected side down.
• If the effusion is > 1 cm, the fluid should be aspirated.
• If the fluid has a pH of < 7, a glucose level of < 2.2 mmol/L, and an LDH content of > 1000 units and is positive on Gram’s staining or culture, it should be drained.
• If frank pus is aspirated, insertion of a large-bore chest tube is recommended.
  • Loculated collections may be manageable with multiple chest tubes placed into loculated compartments.
  • The utility of treatment with intrapleural lytic agents is controversial.
• The goal is eradication of the collection.
  • Follow-up with postdrainage imaging is required to confirm adequate catheter placement and complete pleural fluid drainage.
• Thoracotomy and decortication may be necessary.
• All patients with a complicated pleural effusion, as defined above, should have a consultation with a thoracic surgeon.

Lung abscess

• Incidence
  • Uncommon; 4–5 cases/10,000 hospital admissions
• Risk factors
  • Conditions associated with impaired cough reflex and/or aspiration, such as alcoholism, anesthesia, drug abuse, epilepsy, and stroke
  • Dental caries
  • Bronchiectasis
  • Bronchial carcinoma
  • Pulmonary infarction
• Etiology
  • Most aspiration-associated lung abscesses are due to a combination of aerobic and anaerobic bacteria.
  • On average, 6 or 7 bacterial species are identified in an individual case.
  • Anaerobic bacteria include:
    • Bacteroides fragilis group
    • Bacteroides gracilis
    • Prevotella spp. (intermedia, denticola, melaninogenicus, oralis)
    • Fusobacterium nucleatum
    • Peptostreptococcus spp. (micros, anaerobius, magnus)
  • Aerobic pathogens include:
    • Streptococcus milleri (one of the principal pathogens)
    • S. aureus
    • S. pneumoniae
    • H. influenzae
    • P. aeruginosa
    • E. coli
    • Klebsiella pneumoniae
  • Rarely, S. pneumoniae alone (usually capsular type 3) can cause a lung abscess.
  • In HIV-infected patients, lung abscesses can be due to Pneumocystis, Rhodococcus equi, and Cryptococcus neoformans as well as the bacteria noted above.
• See Lung Abscesses and Empyema for further details, including treatment.

Recurrent pneumonia

• Of patients hospitalized for the treatment of CAP, 10–15% have another episode within 2 years.
• If the recurrence affects the same anatomical location as the previous episode, the most likely cause is an obstructed bronchus due to either a tumor or a foreign body.
• COPD and repeated macroaspiration are the most common causes of recurrent pneumonia.
• Persons without COPD, with pneumonia in a different location from the previous episode, and with no risk factors for aspiration should undergo evaluation for immunodeficiency (including HIV testing), immunoglobulin determination, protein electrophoresis, and enumeration of T and B cells.
• CT of the chest often detects pulmonary anatomical defects (e.g., bronchiectasis) that might be the cause of the recurrence.

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