Study design and outline
The CARdiac suRgery and Oxygen Therapy (CARROT) study is a multicenter, cluster-randomized trial conducted in three tertiary hospitals in Seoul, South Korea, from August 2019 to August 2021. This study was approved by the local ethics committees of the three participating hospitals (the Institutional Review Board of Seoul National University Hospital [SNUH], no. 1902-021-1008; the Institutional Review Board of Asan Medical Center [AMC], no. 2019–0818; and the Severance Hospital Institutional Review Board, no. 4-2020-0741), and the protocol was registered at ClinicalTrials.gov (identifier, NCT03945565). All patients enrolled in this study provided written informed consent. The present study was conducted in compliance with the Declaration of Helsinki and adhered to the CONSORT guidelines.