Diagnosis and treatment of nosocomial pneumonia in ALI/ARDS patients

Abstract

Ventilator-associated pneumonia (VAP) is a common complication of the acute respiratory distress syndrome (ARDS) or acute lung injury (ALI), often leading to the development of sepsis, multiple organ failure, and death. However, the diagnosis of pulmonary infection in patients with ARDS/ALI is often difficult: the systemic signs of infection, such as fever, tachycardia, leukocytosis are nonspecific findings in such patients; a variety of causes other than pneumonia can explain asymmetric consolidation in patients with ARDS and marked asymmetry of radiographic abnormalities has also been reported in patients with uncomplicated ARDS. In 2003, physicians in charge of these patients have to identify patients with true bacterial lung infection, to select appropriate initial antibiotic therapy, to adjust therapy as soon as possible, and to withhold antibiotics in patients without VAP. To do that, a bacteriological strategy based on the use of quantitative cultures of specimen obtained with fibreoptic bronchoscopy performed before initiation or modification of antibiotic treatment seems better than a strategy based on clinical evaluation alone, lowering antibiotic consumption and improving outcome. When bronchoscopy is not available or contraindicated, a nonbronchoscopic strategy or a clinical strategy with re-evaluation 3 days after initiation of treatment may be used. Antimicrobial treatment of VAP is a complex issue. Some general principles can be helpful for the selection of initial treatment: knowledge of most frequently identified responsible pathogens and their susceptibility patterns in the unit; prior duration of hospitalisation; previously prescribed antibiotics; information obtained by direct examination of pulmonary secretions; antibacterial activity and pharmacodynamic characteristics of antibiotics that could be used to treat this infection. Appropriateness of initial antimicrobial therapy is probably a major prognostic factor for patients with ventilator-associated pneumonia. Thus, before new antiboitics are administered, reliable pulmonary specimens must be obtained for direct examination and cultures.