Severe community-acquired pneumonia.

Severe CAP is a life-threatening condition defined by the presence of respiratory failure or symptoms of severe sepsis or septic shock. It accounts for approximately 10% of hospitalized patients with CAP. The majority of patients with severe pneumonia have underlying comorbid illnesses, with COPD, alcoholism, chronic heart disease, and diabetes mellitus being the most frequent. S. pneumoniae, Legionella spp, GNEB (especially K. pneumoniae), H. influenzae, S. aureus/spp, Mycoplasma pneumoniae, respiratory viruses (especially influenza viruses), and P. aeruginosa represent the most important causative organisms of severe CAP. Rapid initiation of appropriate antimicrobial treatment is crucial for a favorable outcome. Initial antimicrobial treatment should be based on an epidemiological (empiric) approach. Microbial investigation may be helpful in the individual case but is probably more useful to define local antimicrobial policies based on local epidemiologic and susceptibility patterns. Mortality rates range from 21% to 54%. The most important prognostic factors include general health state of the patient, appropriateness of initial antimicrobial treatment, and the existence of bacteremia, as well as factors reflecting severe respiratory failure, severe sepsis, septic hypotension or shock, and the extent of infiltrates in chest radiograph. Initial antimicrobial treatment should consist of a second (or third) generation cephalosporin and erythromycin. Modifications of this basic regimen should be considered in the presence of distinct comorbid conditions and risk factors for distinct pathogens. Promising new approaches of nonantimicrobial treatment, including noninvasive ventilation, treatment of hypoxemia, and immunomodulation, are under investigation.