The impact of late-onset ventilator-associated pneumonia on mortality in a Saudi-Arabian hospital

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Introduction

Ventilator-associated pneumonia (VAP) has been recognized as a major factor affecting mortality in intensive care units (ICU). This study compared the relative impact on mortality of early- versus late-onset VAP in an adult medical surgical ICU of a 550-bed tertiary care hospital in Riyadh, Saudi Arabia.

Methods

All patients mechanically ventilated for more than 48 h between November 1996 and December 1997 were included prospectively. VAP was diagnosed according to the definition of the Center for Disease Prevention and Control (CDC), Atlanta. Early- or late-onset VAP was defined respectively as the occurrence of VAP within or after five days of intubation. Pathogens isolated were compared between the two groups. The mortality in the two groups were also compared using univariate and multivariate (logistic regression) analysis.

Results

A total of 202 patients were included in the study. Our incidence density rate of VAP was 16.8 per 1000 person days of ventilation. Fifty-one patients (25.2%) developed VAP, of whom 22 (43.1%) were late-onset. The mortality rates for the early- and late-onset VAP groups were 10.3% (95% CI=2.7 to 28.5%) and 36.4% (95% CI=18.0 to 59.2%), respectively. In a univariate analysis, the relative risk of mortality in the latter group was 3.5 (95% CI=1.1 to 11.7; P=0.029). S. aureus was significantly more common in early- compared to late-onset VAP (44.8% vs 13.9%; P=0.02), while Acinetobacter was more common in late- compared to early-onset VAP (40.9% vs 17.1%; P=0.06). In the logistic regression in which adjustment was made for the effects of pathogens, age and the administration of H₂ receptor antagonists, late-onset VAP remained significantly associated with mortality (risk ratio=6.0, 95% CI =1.1 to 33.9; P=0.042).

Conclusion

Our study shows significant association of lateonset VAP with mortality. This supports what has been observed in previous studies. It is possible to use the time of occurrence of VAP as an important indicator of mortality, and may be used to identify `at risk' patients and initiate more aggressive therapy at an earlier stage.