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The effect of late-onset ventilator-associated pneumonia in determining patient mortality
M H Kollef1, P Silver, D M Murphy
1Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
Study Objective:
To determine whether the development of late-onset ventilator-associated pneumonia (VAP) is associated with an increased risk of hospital mortality.
Design:
Prospective cohort study.
Setting:
ICUs of two university-affiliated teaching hospitals.
Patients:
Three hundred fourteen patients admitted to an ICU who required mechanical ventilation for greater than 5 days.
Interventions:
Prospective patient surveillance and data collection.
Measurements:
The primary outcome measures were the development of late-onset VAP (ie, occurring > 96 h after intubation) and hospital mortality.
Results:
Late-onset VAP was observed in 87 patients (27.7%). Thirty-four (39.1%) patients with late-onset VAP died during hospitalization compared with 85 patients (37.4%) without late-onset VAP (relative risk, 1.04; 95% confidence interval [CI], 0.76 to 1.43). Twenty patients (6.4%) developed late-onset VAP due to a "high-risk" pathogen (ie, Pseudomonas aeruginosa, Acinetobacter sp, Xanthomonas maltophilia) with an associated mortality rate of 65%. Stepwise logistic regression analysis identified five variables as independent risk factors for hospital mortality (p < 0.05): an organ system failure index of 3 or greater (adjusted odds ratio [AOR], 3.4; 95% CI, 2.0 to 5.8; p < 0.001), having a nonsurgical diagnosis (AOR, 2.1; 95% CI, 1.3 to 3.6; p = 0.002), a premorbid lifestyle score of 2 or greater (AOR, 1.8; 95% CI, 1.1 to 2.9; p = 0.015), acquiring late-onset VAP due to a "high-risk" pathogen (AOR, 3.4; 95% CI, 1.2 to 10.0; p = 0.025), and having received antacids or histamine type-2 receptor antagonists (AOR, 1.7; 95% CI, 1.0 to 2.9; p = 0.034). Additionally, we found the occurrence of late-onset VAP due to high-risk pathogens to be the most important predictor of hospital mortality among patients developing VAP (AOR, 5.4; 95% CI, 2.8 to 10.3; p = 0.009).
Conclusions:
Nosocomial pneumonia due to certain high-risk microorganisms is an independent risk factor for hospital mortality among patients requiring prolonged mechanical ventilation. We suggest that future investigations of late-onset VAP stratify patient outcomes according to the distribution of high-risk pathogens when reporting their results.