Introduction Impaired cerebral autoregulation is associated with postoperative ischaemic brain injury and often occurs in patients with carotid artery stenosis. Adequate cerebral perfusion should therefore be maintained during carotid endarterectomies. Whether guiding intraoperative blood pressure to the Cerebral Oximetry Index (a measure of cerebral perfusion adequacy) reduces postoperative cerebral ischaemia remains unclear.Methods and analysis We plan a dual-centre randomised blinded trial. A total of 560 patients having elective carotid endarterectomy will be randomly assigned to guided versus routine haemodynamic management. In patients randomised to guided management, mean arterial pressure will be titrated to maintain a normal cerebral oximetry index. In the routine care group, mean arterial pressure will be targeted to within 20% of individual preoperative baseline values. The primary outcome will be the incidence of new ischaemic brain injury within 3 days after surgery assessed by brain imaging, with or without clinical symptoms. Secondary outcomes include the incidence of postoperative delirium, cognitive function and pain severity.Ethics approval and dissemination The study protocol (V.1.2, 1 January 2025) has been approved by the Medical Ethics Committee of Beijing Tiantan Hospital, Capital Medicine University (KY2024-049-03) and Xuanwu Hospital, Capital Medical University (LYS2025-023-001). The findings of the study will be disseminated in a peer-reviewed journal and at a scientific conference.Trial registration number NCT06406842.