Background and objective:
Eight to 12% of patients admitted to hospitals in the European Union (EU) experience adverse events. Surgical-related adverse effects are among the most common in-hospital adverse events, with most surgical errors occurring outside the operating room. Although no set of outcomes has yet been defined for a comprehensive analysis of this phenomenon, it is crucial to standardise a minimum set of outcomes, a Core Outcome Set (COS), to allow for benchmarking across EU countries. This study aims to develop a relevant and feasible COS for patient safety in perioperative care, including patient-relevant data.

Methods:
We will follow a multimethod approach based on COS-STAD recommendations. First, an initial list of outcomes (ILO) will be developed by conducting an umbrella review of outcomes on patient safety in perioperative care in surgical adult patients. Next, this umbrella review will be complemented by outcomes identified in a systematic review of Clinical Practice Guidelines and an umbrella review of non-clinical interventions to improve perioperative patient safety. Then, the ILO will be prioritised by healthcare professionals and patient representatives according to the importance and feasibility of each outcome in a two-round eDelphi process by April 2023. The final list of outcomes (FLO) will be defined in a consensus conference by the same stakeholders.

Results:
As this study is still undergoing, the results are not yet available. The FLO will be presented in a summary of findings table, containing, for each of the up to 50 prioritised outcomes, the outcome name, definition, and domain.

Conclusion:
This COS will contribute to improving the monitoring and evaluation of patient safety practices in perioperative care and, thus, the quality of care and healthcare decision-making. Additionally, this COS will help standardise outcome reporting in perioperative patient safety and facilitate the comparison of data across studies.