Study objective: To determine the impact of antibiotic treatment of ventilator-associated pneumonia (VAP) on survival.
Design: Decision analysis.
Patients: A hypothetical cohort of immunocompetent patients receiving mechanical ventilation who have suspected bacterial pneumonia. The analysis was performed separately for the following diagnostic techniques: clinical criteria, bronchoscopic protected specimen brush (PSB), and nonbronchoscopic protected BAL (pBAL). Additional factors accounted for in the analysis included the presence or absence of prior antibiotic use, mortality of antibiotic-treated and untreated pneumonia, mortality attributable to VAP, development of antibiotic resistance, and mortality due to adverse drug reactions.
Measurements and results: The overall survival of patients who receive antibiotic therapy was compared to survival if antibiotic therapy had been withheld. Antibiotic treatment of clinically diagnosed VAP was associated with lower overall survival than withholding treatment. Antibiotic treatment of VAP diagnosed by invasive (PSB) or semi-invasive (pBAL) techniques was associated with better survival than withholding treatment, although withholding antibiotic therapy was favored as the mortality rate of antibiotic-treated VAP approached 70%.
Conclusions: Invasive or semi-invasive diagnostic techniques should be used to diagnose VAP, guide therapy, and thereby potentially improve survival. A prospective, randomized trial assessing outcome according to diagnostic technique is needed.