Nosocomial Pneumonia

Abstract

Approximately 300,000 cases of hospital acquired (nosocomial) pneumonia are diagnosed yearly in the U.S. They are defined as an infection of the lung parenchyma that was neither present nor incubating at the time of hospital admission and became manifest 72 hours after admission. This definition, however, does not include outpatients or patients that develop pneumonia after discharge. Nosocomial pneumonias occur at a rate of 0.6–1.0 percent of hospital admissions in the U.S. and are associated with a high morbidity; they have the highest mortality of all types of nosocomial infection. To prevent this severe complication, it is critical to understand epidemiology and pathogenesis; several predisposing endogenous host factors and exogenous conditions have been identified. The former include age > 60, debility, depressed consciousness, immune deficiency, organ failure, COPD, smoking, and low serum albumin. Exogenous factors include recent thoracic or upper abdominal surgery, major trauma as well as prolonged duration of an operation and ICU admission. Medications such as steroids, immunosuppressive drugs, previous antibiotic therapy and H₂-blocker therapy may also predispose to hospital acquired pneumonia. Most cases occur in non-ventilated patients, but the rate of pneumonia in ventilated patients is 20-fold increased.