Study protocol
In all hospitals, anesthesia was induced with intravenous administration of midazolam and sufentanil or remifentanil and maintained using a target-controlled infusion of propofol and remifentanil. The use of 100% oxygen was allowed during preoxygenation at anesthesia induction. After tracheal intubation, MV was initiated with 30% or 80% oxygen as allocated. If oxygen saturation decreased below 93–94% or arterial oxygen partial pressure (PaOComplete coronary revascularization was performed off-pump whenever feasible. Otherwise, routine anesthetic/intraoperative and postoperative care procedures in each participating hospital were not regulated by the protocol of this study, except for the above-mentioned intraoperative FiO