Patients
Patients were included in the primary trial if they were older than 40, scheduled to have major surgery of expected duration > 2 hours and anticipated to receive invasive arterial pressure monitoring as part of their routine care. Patients were excluded if they were pregnant; scheduled to have cardiac, thoracic or intracranial neurological surgery; or if they had been previously enrolled in the trial. The patients undergoing laparoscopic surgery included in this analysis comprise a pre-specified subgroup defined prior to randomisation [