Pneumonia in the intensive care unit setting

Nosocomial pneumonia is a common and serious occurrence in the ICU. It most often results from aspiration of oropharyngeal secretions that have become colonized with pathogenic enteric gram-negative bacilli. Colonization occurs in association with acute and chronic illness and particularly with therapy that includes nasogastric or endotracheal tubes, H₂ blocking antacid drugs, or antibiotics; aspiration is increased by anesthesia, sedative drugs, and upper airway instrumentation. The diagnosis of ICU-acquired pneumonia is complicated greatly by the nonspecificity of clinical and laboratory data, and the difficulty in distinguishing the organisms producing infection from those merely colonizing the airway when using routine culture techniques. Among specialized diagnostic techniques, quantitative culture of specimens obtained with the protected sampling brush offers the most promise in establishing a specific microbacteriologic diagnosis of nosocomial pneumonia. Empirical treatment with broad spectrum antibiotics is frequently necessary when a specific diagnosis cannot be made. The poor outcome associated with nosocomial pneumonia, regardless of treatment, suggests that methods to prevent dissemination and oropharyngeal colonization of the offending organisms should be emphasized.