Nosocomial pneumonia in the intubated patient: role of gastric colonization.

A high rate of nosocomial pneumonia exists among intubated patients receiving mechanical ventilation. Retrograde colonization of the oropharynx and trachea with bacteria from the stomach is not widely appreciated in the pathogenesis of pneumonia. Gastric colonization is affected by age, malnutrition, antibiotics, disease of the gastrointestinal tract, and changes in pH. The widespread use of antacids and/or histamine type 2 blockers as prophylaxis against stress bleeding in the ventilated patient may also increase gastric pH and the risk of colonization in the upper gastrointestinal tract. Migration of bacteria between the stomach, oropharynx and trachea in the intubated patient may be a dynamic system involving large numbers of bacteria. The high fatality rate of mechanically ventilated patients with pneumonia, which persists despite treatment of these patients with appropriate antimicrobial therapy, underscores the need for effective measures of prevention. Preventive measures include the appropriate use of antibiotics, proper decontamination of respiratory therapy equipment, the cautious use of drugs that alter the natural gastric acid barrier, or, possibly, the selective use of antibiotics to prevent or reduce gastric, oropharyngeal and tracheal colonization.