Diagnosis of ventilator-associated pneumonia.

In this issue of the Journal, Heyland et al., writing for the Canadian Critical Care Trials Group, report the results of a multicenter, randomized trial comparing the use of bronchoalveolar lavage and endotracheal aspiration for the diagnosis of ventilator-associated pneumonia.1 This study was part of a larger 2-by-2 factorial design also comparing empirical antimicrobial monotherapy (a carbapenem) and combination therapy (a carbapenem plus a fluoroquinolone). The authors conclude that bronchoalveolar lavage and endotracheal aspiration are associated with similar clinical outcomes and similar overall use of antibiotics. However, several important limitations of the study must be appreciated in order to place it into proper context. Heyland et al. restricted the patient population and the pathogens evaluated in their study. Of the 2531 screened patients, 307 (12.1%) were excluded because they were already colonized or had a respiratory tract infection with an organism not sensitive to one of the study drugs, and 706 (27.9%) were excluded because they were immunocompromised, had already received one of the study drugs, or had a chronic disease. Therefore, at least 40% of the screened patients who were excluded had risk factors for colonization or infection with potentially antimicrobial-resistant bacteria. Unfortunately, these exclusions probably represent the majority of patients undergoing real-time evaluation for suspected ventilator-associated pneumonia.2-5 Initial administration of an appropriate antimicrobial regimen (i.e., one to which the pathogens are sensitive, on the basis of in vitro susceptibility testing) in patients with suspected ventilator-associated pneumonia should be regarded as one of the primary determinants of in-hospital outcome. Use of an initial antimicrobial regimen that is inappropriate for the microorganisms causing ventilator-associated pneumonia has been associated with a significantly greater risk of death than use of an appropriate initial regimen.6,7 These findings strongly suggest that initial antimicrobial therapy for ventilator-associated pneumonia and other serious infections should be selected according to the presence or absence of risk factors for infection associated with health care (e.g., recent hospitalization, admission from a chronic care environment, current hemodialysis, immunocompromised state, late-onset infection, or prior use of antimicrobial agents during the current period of hospitalization).5,8 Initial antimicrobial regimens in patients with suspected ventilator-associated pneumonia who have these risk factors should appropriately treat potentially resistant pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa.8 The guidelines for the management of nosocomial pneumonia, recently published by the American Thoracic Society and the Infectious Diseases Society of America, propose a de-escalation approach to treatment that attempts to address the need for balancing appropriate initial antimicrobial therapy and emerging antibiotic resistance.8 In patients with clinically suspected ventilator-associated pneumonia, specimens should be obtained from the respiratory tract for microbiologic processing, followed by the timely administration of an empirical antimicrobial regimen selected according to the presence or absence of risk factors for infection with antimicrobialresistant bacteria. Microorganism identification and antibiotic susceptibility testing should also be conducted so that the use of antimicrobial agents can be deescalated when appropriate. An important caveat in applying this guideline is that