Multicenter prospective study of ventilator-associated pneumonia during acute respiratory distress syndrome: Incidence, prognosis, and risk factors

We investigated the incidence, risk factors for, and outcome of ventilator-associated pneumonia (VAP) in patients with acute respiratory distress syndrome (ARDS). We compared 134 patients with ARDS with 744 patients without ARDS on mechanical ventilation. Fiberoptic bronchoscopic examination and quantitative bacterial cultures (protected brush or catheter sampling [threshold: 10 3 cfu/ml], or bronchoalveolar lavage [threshold: 10 4 cfu/ml]) were used to diagnose pneumonia. VAP occurred in 49 patients (36.5%). The incidence of pneumonia was 23% (173 of 744 patients) among patients without ARDS (p , 0.002). Nonfermenting gram-negative rods caused significantly more pneumonia in ARDS patients. Mortality rates were identical in ARDS patients with (28 of 49 patients, 57%) and without (50 of 85 patients, 59%) pulmonary infection (p 5 0.8). VAP resulted in a considerable increase in attributable time on mechanical ventilation of both the overall population of ARDS patients and of survivors. Both the use of sucralfate (adjusted odds ratio [OR]: 4.42; 95% confidence interval [CI]: 2.01 to 9.7, p 5 0.0002) and the duration of exposure to sucralfate (adjusted OR: 1.206; 95% CI: 1.095 to 1.328, p 5 0.0002) were associated with an increased risk of VAP during ARDS. VAP considerably prolongs the time on mechanical ventilation without affecting survival. Patients given sucralfate may be at greater risk of developing pulmonary infection during ARDS. Acute respiratory distress syndrome (ARDS) has been a challenging organ-failure condition with a high mortality rate from its first description as a syndrome in 1967. Nosocomial pneumonia is a frequent complication of ARDS. Although the impact of nosocomial pneumonia on the outcome of mechanically ventilated patients remains controversial (1, 2), it may play a key role by worsening hypoxemia and causing sepsis, multiple organ failure, and death. Previous clinical and histologic studies have found that ventilator associated pneumonia (VAP) can affect between 20% and 75% of patients dying of ARDS (3‐6). However, it is difficult to diagnose nosocomial pulmonary infection in patients with ARDS because the clinical criteria (fever, leucocytosis, and purulent tracheal secretions) for VAP are nonspecific, and since all patients with ARDS have bilateral diffuse infiltrates on chest radiographs, radiologic changes may be very difficult to detect. Most previous studies have used the bacteriologic results of tracheal aspiration, a technique with poor specificity because of tracheal colonization during mechanical ventilation, for diagnosing such pulmonary infection. Recently, four groups of investigators studied the incidence of pulmonary superinfection during ARDS and obtained conflicting results for the exact incidence of VAP. All of these previous studies were conducted at single centers, and none examined the potential risk factors for acquisition of VAP during ARDS (7‐10). We therefore undertook this prospective multicenter study to: ( 1 ) investigate the incidence of microbiologically documented VAP in a large number of patients with ARDS; ( 2 ) compare the mortality and morbidity in ARDS patients with and without VAP; and ( 3 ) evaluate risk factors for pneumonia in these patients. The diagnosis of VAP was based on quantitative cultures of samples obtained with the protected specimen brush (PSB), bronchoalveolar lavage (BAL), or plugged telescopic catheter (PTC) techniques via fiberoptic bronchoscopy. Sucralfate was strongly associated with an increased incidence of VAP in this study. This finding seems to contradict widely held opinion (11, 12).