Planned statistical analysis summary.

Introduction
The Fragility Index (FI) and the FI family are statistical tools that measure the robustness of randomized controlled trials (RCT) by examining how many patients would need a different outcome to change the statistical significance of the main results of a trial. These tools have recently gained popularity in assessing the robustness or fragility of clinical trials in many clinical areas and analyzing the strength of the trial outcomes underpinning guideline recommendations. However, it has not been applied to perioperative care Clinical Practice Guidelines (CPG).
Objectives
This study aims to survey clinical practice guidelines in anesthesiology to determine the Fragility Index of RCTs supporting the recommendations, and to explore trial characteristics associated with fragility.
Methods and analysis
A methodological survey will be conducted using the targeted population of RCT referenced in the recommendations of the CPG of the North American and European societies from 2012 to 2022. FI will be assessed for statistically significant and non-significant trial results. A Poisson regression analysis will be used to explore factors associated with fragility.
Discussion
This methodological survey aims to estimate the Fragility Index of RCTs supporting perioperative care guidelines published by North American and European societies of anesthesiology between 2012 and 2022. The results of this study will inform the methodological quality of RCTs included in perioperative care guidelines and identify areas for improvement.