1 From the College of Medicine and Veterinary Medicine, University of Edinburgh (EC), Department of Anaesthesia, Critical Care and Pain Medicine, Royal Infirmary of Edinburgh (SG, ABD, DCR, TSW, MAG), Edinburgh Critical Care Research Group (ABD, AL, HD, TSW, MAG), Edinburgh Clinical Trials Unit, Usher Institute of Population Sciences and Informatics, University of Edinburgh (CK), Department of Trauma and Orthopaedics (TOW), Geriatric Medicine, University of Edinburgh, Royal Infirmary of Edinburgh (AMJML) and BHF Centre for Cardiovascular Sciences, University of Edinburgh, Edinburgh, UK (NLM).