Study identification

Three databases were searched for relevant studies from 1 March 2012, the Cochrane Central Register of Controlled Trials (CENTRAL) The Cochrane Library until 17 November 2017, Issue 10; MEDLINE (Ovid) from 1950 to 17 November 2017; and EMBASE [Ovid] from 1950 to 17 November 2017. The search was not restricted for trials by date, language, or publication status. We also searched the reference lists of relevant reviews, published articles, available online conference proceedings (Annual Meetings of the American Society of Anesthesiologists, Canadian Anesthesiologists Society, European Society of Anaesthesiology, American Society of Hematology, European Hematology Association, Society of Critical Care Medicine, Society of Cardiovascular Anesthesiologists, and European Association of Cardiothoracic Anaesthesiology), and practice guidelines (American Society of Anesthesiologists, National Institute for Clinical Excellence, and Society of Thoracic Surgeons/Society of Cardiovascular Anesthesiologists), as well as the reference lists of all included trials for further studies. The full search criteria can be found in the Supplementary material online.