Risk factors for Ventilator- Associated Events in patients under invasive mechanical ventilation in the ICU

Abstract

Background: Recently, the Centers for Disease Control and Prevention – (CDC), released new surveillance definitions to expand the scope of surveillance from Ventilator Associated Pneumonia – (VAP) to Ventilator Associated Events – (VAEs). The VAEs framework is wider than the framework of VAP and in addition, VAEs are more frequent and strongly associated with adverse patient outcomes. Therefore, the identification of risk factors for VAE is needed so as to create appropriate prevention strategies.

Aim: The aim of this study was to identify potentially modifiable risk factors for VAE.

Method: We conducted a prospective “case – control” study in 4 ICUs in the region of Attica from to 1/1/2018 to 1/1/2020. During the study period , 500 patients aged ≥ 18 years were under invasive mechanical ventilation for ≥ 4 days, 207 from whom had VAE. Among VAE patients 163 were successfully matched to 163 “controls” without VAE on the basis of age (± 5 years), sex, Charlson Score (± 2 points), hospital and the duration of mechanical ventilation before VAE onset at VAE patients. For the diagnosis of VAE we used the CDC definitions as published in 2018. Univariate and Multivariate Conditional Logistic Regression Analysis was performed to account for matching. All analyses were performed using SPSS (Statistical Package for Social Sciences) v. 24.0.

Results: The incidence density of VAE in our study was 20,5/1000 ventilator days or 20,5/ 100 episodes of mechanical ventilation. Median time to VAE was 6 days. On multivariable conditional logistic regression, significant risk factors for VAE were daily positive fluid balance, (OR=11,71 , CI=4,25-32,30 , p<0,001), transfusion with Red Blood Cells (OR=5,36 , CI=1,73-16,59 , p=0,004), sedation with propofol (OR=4,01 , CI=1,51-10,64 , p=0,005), exposure to paralytics (OR=3,62 , CI=1,30-10,06 , p=0,014) and exposure to mandatory modes of ventilation (OR=3,26 , CI=1,46-7,29 , p= 0,004).

Conclusions: Our study indicates 5 significant risk factors for VAE that could be used as element for the development of a new ventilator bundle. It is mentioned however, that randomized trials are needed so as to clarify the picture of VAE and improve patients’ outcomes.