The study protocol was approved by the ethics committee at Monash University, which was the coordinating center, and at each participating institution. The protocol and statistical analysis plan are available at NEJM.org. Prior informed written consent or delayed consent was obtained from all patients or their legal surrogates. The trial was overseen by an independent data and safety monitoring committee. Scvo2 monitors were loaned to participating sites by Edwards Lifesciences, which had no other role in the conduct of the study.