Attributable mortality of ventilator-associated pneumonia : replicating findings, revisiting methods

Rationale: Estimating the impact of ventilator-associated pneumonia (VAP) from routinely collected ICU data is methodologically challenging. Objectives: We aim to replicate earlier findings of limited VAP-attributable ICU mortality in an independent cohort. By refining statistical analyses, we gradually tackle different sources of bias. Methods: Records of 2,720 adult patients admitted to Ghent University Hospital ICUs (2013—2017) and receiving mechanical ventilation within 48 hours following admission were extracted from linked ICIS and COSARA databases. The VAP-attributable fraction of ICU mortality was estimated using a competing risk analysis that is restricted to VAP-free patients (approach 1), accounts for VAP onset by treating it as either a competing (approach 2) or censoring event (approach 3), or additionally adjusts for time-dependent confounding via inverse probability weighting (approach 4). Results: Two hundred ten patients (7.7%) acquired VAP. Based on benchmark approach 4, we estimated that (compared to current preventive measures) hypothetical eradication of VAP would lead to a relative ICU mortality reduction of 1.7% (95% confidence interval: -1.3—4.6) by day 10 and of 3.6% (95% confidence interval: 0.7—6.5) by day 60. Approaches 1—3 produced estimates ranging from -0.7 to 2.5% by day 10, and from 5.2 to 5.5% at day 60. Conclusions: In line with previous studies using appropriate methodology, we found limited VAP-attributable ICU mortality given current state-of-the-art VAP prevention measures. Our study illustrates that inappropriate accounting of the time-dependency of exposure and confounding of its effects may misleadingly suggest protective effects of early-onset VAP and systematically overestimate attributable mortality.

Publication year:2021

Accessibility:Open