NOSOCOMIAL PNEUMONIA IN PATIENTS WITH ACUTE RESPIRATORY-DISTRESS SYNDROME

To describe the epidemiologic and microbial aspects of ventilator-asso ciated pneumonia (VAP) in patients with acute respiratory distress syn drome (ARDS), we prospectively evaluated 243 consecutive patients who required mechanical ventilation (MV) for greater than or equal to 48 h , 56 of whom developed ARDS as defined by a Murray lung injury score > 2.5. We did this with bronchoscopic techniques when VAP was clinicall y suspected, before any modification of existing antimicrobial therapy . For all patients, the diagnosis of pneumonia was established on the basis of culture results of protected-specimen brush (PSB) (greater th an or equal to 10(3) cfu/ml) and bronchoalvelolar lavage fluid (BALF) (greater than or equal to 10(4) cfu/ml) specimens, and direct examinat ion of cells recovered by bronchoalveolar lavage (BAL) (greater than o r equal to 5% of infected cells). Thirty-one (55%) of the 56 patients with ARDS developed VAP for a total of 41 episodes, as compared with o nly 53 (28%) of the 187 patients without ARDS for a total of 65 episod es (p = 0.0005). Only 10% of first episodes of VAP in patients with AR DS occurred before Day 7 of MV, as compared with 40% of the episodes i n patients without ARDS (p = 0.005). All but two patients with ARDS wh o developed VAP had received antimicrobial treatment (mostly with broa d-spectrum antibiotics) before the onset of infection, as compared wit h only 35 patients without ARDS (p = 0.004). The organisms most freque ntly isolated from patients with ARDS and VAP were methicillin-resista nt Staphylococcus aureus (23%), nonfermenting gram-negative bacilli (2 1%), and Enterobacteriaceae (21%). These findings confirm that microbi ologically provable VAP occurs far more often in patients with ARDS th an in other ventilated patients. Because these patients are often trea ted with antibiotics early in the course of the syndrome, the onset of VAP is frequently delayed after the first week of MV, and is then cau sed mainly by methicillin-resistant S. aureus and other multiresistant microorganisms.