Introduction Adverse neurological complications, including postoperative delirium (POD) and stroke, remain one of the major risks after cardiac surgery. A lack of comprehensive knowledge about their causes and neuroprotective strategies has hindered the development of effective interventions to reduce these events. Personalised cerebral autoregulation (CA)-oriented blood pressure monitoring aims to identify blood pressure targets tailored to each individual patient, thereby reducing brain injury. The PRECISION study aims to assess whether perioperative duration and magnitude of mean arterial pressure (MAP) deviation from an individual’s CA limits are associated with adverse neurological complications.

Methods and analysis This international, multicentre, prospective cohort study is conducted at two Swiss and one British hospital. Patients aged 65 years or older undergoing elective primary or re-operative coronary artery bypass graft and/or valvular and/or ascending aorta surgery requiring cardiopulmonary bypass are included. Preoperatively, the patient’s baseline of physical, cognitive and mental status is established. Intraoperatively, near-infrared spectroscopy (NIRS) and transcranial Doppler (TCD) are recorded in real-time to generate NIRS-derived and TCD-derived CA indices. The primary endpoint is POD, assessed daily on postoperative days 0 to 7 or up to discharge, whichever occurs earlier with the 3D-Confusion Assessment Method (3D-CAM) or CAM-Intensive Care Unit. Secondary endpoints include a composite neurological outcome of POD and overt stroke, postoperative neurocognitive disorders, major morbidity and mortality. Associations between neurologic outcomes, neurobiomarkers and genetic variation will be explored.

A total of 500 participants is required to achieve 90% power to find a statistically significant effect of the area under the curve MAP<lower limit of CA (LLA) on the risk of POD at the 5% level. This includes adjustment for potential confounders and for the inability to determine the LLA.