Development of C ore O utcome S ets for trials on the management of A trial fi B rill A tion in C ritically U nwell patient S (COS-ABACUS): a protocol.

The study has been approved by the University of Liverpool ethics committee (Ref: 11 256, 21 June 2022), with a formal consent waiver and assumed consent. We will disseminate the finalised COS via national and international critical care organisations and publication in peer-reviewed journals.