Risk Factors for Preventing Ventilator-Associated Events in Children: Have We Recognized Them Yet?*

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In this issue of the Pediatric Critical Care Medicine, Guess et al (1) aim to identify potential new risk factors for ventilator-associated condition (VAC) and infection-related ventilator-associated complication (IVAC), so that further prevention strategies can be developed. They designed a matched case-control study and performed univariate and multivariate logistic regression analyses to look for independent risk factors associated with VAC and IVAC. The population included were all patients admitted to a single PICU who received invasive mechanical ventilation for more than 48 hours. The authors reported 40 IVAC and 30 VAC cases that were matched to 140 controls. Matching was adequate with regard to age, immunocompromised status, and ventilator days to the event. Nevertheless, both the VAC and IVAC patients had significantly higher Pediatric Index of Mortality 2 (PIM 2) scores than control patients (p < 0.05). Therefore, cases were significantly sicker than the controls (1).
The authors then demonstrated in the univariate analysis that the development of acute kidney injury (AKI), increased peak cumulative fluid overload, mean peak inspiratory pressure (PIP), mean Paw, use of a neuromuscular blockade (NMB) infusion, and steroid exposure were associated with VAC. Also, in the univariate analysis, diagnosis of AKI or NMB infusion were associated with IVAC. After adjusting for PIM 2 score in the multivariate logistic regression analysis, the mean PIP continued to be associated with VAC (odds ratio [OR], = 1.12 [95% CI, 1.02–1.22]), as was the presence of AKI (OR, 2.85 [95% CI, 1.43–5.66]). AKI also continued to be associated with IVAC (OR, 2.36 [95% CI, 1.03–5.4]), and the use of NMB infusions was also found to be associated with IVAC (OR, 3.19 [95% CI, 1.17–8.68]). Consequently, the authors concluded that AKI and mean PIP were independent risk factors for VAC and that AKI and NMB infusion were independent risk factors for IVAC (1).
A core principle of medical practice is to base decisions on the highest quality, objectively derived scientific data, but determining whether data meet these conditions might be difficult. Although randomized, controlled trials have long been presumed to be the ideal source for this kind of data, other methods of obtaining evidence for decision making are receiving increased interest, for example, observational studies (2). Bearing in mind that no study design is flawless, and conflicting findings can emerge from all types of designs, my first comment on the study by Guess et al (1) is that we, as readers, should not reject case-control studies simply because of the design type and we should not avoid doing a critical reading.
Ventilator-associated event (VAE) surveillance was introduced in 2013, replacing surveillance for ventilator-associated pneumonia in adult patients (3). Most VAEs are due to pneumonia, pulmonary edema, atelectasis, or acute respiratory distress syndrome. Although some of these conditions might be prevented, VAE preventability has not been well established. This is VAE’s most important limitation, and additional studies are needed to identify preventable risk factors that allow for the development strategies to reduce the rate of this event (4). Recognizing factors associated to VAE is also significant to critically ill children. It has been reported in a retrospective single-center cohort study that VAE patients have worse outcomes (e.g., increased hospital mortality and longer ventilator days) (5). Considering these issues, my following comment on the article by Guess et al (1) is that authors should be acknowledged for attempting to contribute evidence on this topic.
However, as most things are not straightforward, I think the authors did not achieve substantial answers, and we remain in the usual position of having to tolerate uncertainty (6).

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