Ventilator-associated pneumonia in a tertiary care ICU: analysis of risk factors for acquisition and mortality

Abstract

Objective: To investigate the incidence, risk factors and mortality of ventilator-associated pneumonia (VAP) in intensive care unit (ICU) patients.

Design: Prospective, observational, population-based study.

Setting: The medical (14-bed) and surgical ICU (26-bed) of the Ghent University Hospital.

Methods: All 1295 patients admitted to the ICU during 4 three-month periods between 1996 and 1998 were included. A set of demographic and clinical variables were collected at the day of admission and during the ICU course.

Results: The incidence of VAP among ICU patients ventilated at least 48 hours was 23.1%. The mean time to the development of VAP was 9.6 days with a median of 6 days. In the population of patients ventilated for at least 48 hours, a comparison was made between patients with (n = 89) and without VAP (n = 296). Patients with VAP had a significant longer ICU stay, with a longer ventilation dependency. Logistic regression analysis identified admission diagnosis other than trauma (OR: 0.51, 95% CI: 0.29-0.89; p = 0.02) and the length of ICU stay (OR: 1.05, 95% CI: 1.03-1.07; p < 0.001) to be independently associated with the acquisiton of VAP. In comparison with the total study population, patients with VAP had a higher ICU mortality (20.2% vs. 12.0%; p = 0.04), but not in the cohort group of patients at risk for VAP (ventilated > 48 hours)(20.2% vs. 31.3%; p = 0.03). The factors independently associated with death were higher SAPS II scores (OR 1.02, 95% CI: 1.003-1.032; p = 0.02), an admission diagnosis other than trauma (OR 0.36, 95% CI: 0.17-0.75; p = 0.006) and length of ICU stay (OR 0.97, 95% CI: 0.946-0.995; p = 0.02). This model did not recognize VAP as an independent predictor of death (OR 0.79, 95% CI: 0.41-1.53; p = 0.492).

Conclusions: The incidence of VAP in our ICU is 23.1%. Length of ICU stay and an admission diagnosis other than trauma are major risk factors for the development of this nosocomial infection. VAP is associated with a high fatality rate. However, after adjustment for disease severity and length of ICU stay, VAP was not identified as an independent predictor of death.