# Arms-Based Meta-Analysis of Microbiological Endpoints of 88 VAP Prevention Studies Using Antimicrobial Versus Non-Antimicrobial Strategies—Towards ‘VAP-Zero’?

## TL;DR

This study compares antimicrobial and non-antimicrobial strategies for preventing ventilator-associated pneumonia and finds that neither approach achieves zero cases.

## Contribution

The study uses arm-based meta-analysis to reveal that antimicrobial interventions do not lead to VAP-zero, a finding not evident from traditional contrast-based analysis.

## Key findings

- Antimicrobial interventions did not achieve VAP-zero overall or for specific pathogens like Staphylococcus aureus.
- Contrast-based and arm-based meta-analyses showed similar effect sizes for VAP prevention interventions.
- Summary VAP incidence in antimicrobial groups was similar to non-antimicrobial groups for all pathogens analyzed.

## Abstract

Background/Objectives: In traditional contrast-based meta-analyses of randomized concurrent controlled trials (RCCTs), topical antibiotic prophylaxis (TAP) appears more effective than either antiseptic-based or non-antimicrobial-based interventions for preventing ventilator-associated pneumonia (VAP). The objective here is to use arm-based methods to determine whether this effectiveness translates towards achieving VAP-zero, both overall and specifically for VAP in association with Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter species among the same RCCTs. Methods: Data were extracted from RCCTs sourced primarily from Cochrane reviews of VAP prevention interventions. Arms-based and contrast-based methods of meta-analyses of the VAP prevention effect size and the VAP incidence per 100 patients receiving mechanical ventilation were obtained using random effects methods. Results: The VAP prevention intervention effect sizes derived by contrast-based versus arms-based meta-analyses were similar for each of the three broad types of interventions. The overall VAP prevention effect of antibiotic-based interventions by contrast-based and arms-based methods were 0.39 (95% confidence interval 0.33 to 0.46; n = 28) versus 0.39 (95% confidence interval 0.32 to 0.47; n = 28), respectively. Surprisingly, the arms-based analysis revealed that the summary VAP incidence, both overall and for each of Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter species within antibiotic intervention groups, were similar to the respective summary incidences within intervention groups of non-antimicrobial RCCTs. Conclusions: VAP-zero, both overall and in association with specific microbial sub-types, has remained elusive using antimicrobial-based interventions. This inference was not evident from a contrast-based analysis.