Patient population
This was a retrospective observational study conducted at a single institution. This study was approved by the Royal Papworth Hospital Research and Development department and the requirement for patient consent waived. All patients undergoing adult cardiac surgery at Royal Papworth Hospital (United Kingdom) between January 2015 to April 2019 were included in this study. Demographic, intra-operative and post-operative outcome data, including return to theatre, mediastinal blood loss, blood product transfusion, and length of hospital and ICU stay was collected prospectively. Mortality information was obtained from the UK national patient administration system.