The interaction of infection and the adult respiratory distress syndrome.
Review
Overview
abstract
Infection, particularly that involving the respiratory tract, is commonly seen in the patient with ARDS. It can be either an etiologic factor leading to the syndrome or a complicating factor leading to a high likelihood of mortality. Pneumonia develops in up to 70% of individuals with ARDS, and when present, converts the syndrome to its most severe and mortal form. In addition, when systemic injury coexists with any type of infection, ARDS will develop with an increased frequency. Nosocomial pneumonia results when upper and lower respiratory tract defenses fail and these sites are overwhelmed by bacteria. Colonization of the oropharynx and tracheobronchial tree, both of which are common in critically ill patients, precedes the development of pneumonia. In the patient with ARDS, all levels of host antibacterial defenses may be impaired, thus accounting for the high incidence of both colonization and pneumonia. These impairments result from the acute lung injury itself, coexisting systemic illnesses, therapeutic interventions, and acquired malnutrition. Once pneumonia develops in the course of acute lung injury, diagnosis is exceedingly difficult and potentially inaccurate. With proper application of the protected specimen brush, inserted bronchoscopically, diagnostic accuracy may improve. Therapy must be undertaken early and with agents directed at likely pathogens, particularly P. aeruginosa and other gram-negative bacilli. In the future, preventive efforts against pneumonia may be effective for the ARDS patient. Strategies that may be effective include hyperalimentation, judicious use of all pharmacotherapy, active and passive antibacterial vaccines, airway microenvironment manipulation, and the use of aerosolized antibiotics.
