PRECISION study: impact of personalised cardiac anaesthesia and cerebral autoregulation on neurological outcomes in patients undergoing cardiac surgery - protocol for an international, multicentre, prospective cohort study.

The PRECISION study requires 500 participants to achieve sufficient statistical power for its primary endpoint.

• A total of 500 participants is required to achieve 90% power to find a statistically significant effect of the area under the curve MAP below the lower limit of cerebral autoregulation (LLA) on the risk of postoperative delirium at the 5% significance level.
• The sample size calculation includes adjustment for potential confounders and for the inability to determine the LLA in some patients.
• The study is conducted at two Swiss hospitals and one British hospital.

The study's primary endpoint is postoperative delirium (POD), assessed daily from postoperative days 0 to 7 or until discharge.

• POD is assessed using the 3D-Confusion Assessment Method (3D-CAM) or CAM-Intensive Care Unit (CAM-ICU), whichever is applicable.
• Assessment occurs daily on postoperative days 0 to 7 or up to discharge, whichever occurs earlier.
• Adverse neurological complications including POD and stroke are described as 'one of the major risks after cardiac surgery.'

Secondary endpoints include a composite neurological outcome, postoperative neurocognitive disorders, major morbidity, and mortality.

• Secondary endpoints include a composite neurological outcome of POD and overt stroke.
• Postoperative neurocognitive disorders are included as a secondary endpoint.
• Associations between neurologic outcomes, neurobiomarkers, and genetic variation will also be explored.

The study uses near-infrared spectroscopy (NIRS) and transcranial Doppler (TCD) to generate intraoperative cerebral autoregulation indices in real time.

• Both NIRS-derived and TCD-derived cerebral autoregulation (CA) indices are generated from intraoperative recordings.
• These indices are used to identify blood pressure targets tailored to each individual patient.
• Personalised CA-oriented blood pressure monitoring aims to identify mean arterial pressure (MAP) targets to reduce brain injury.

The study population is restricted to patients aged 65 years or older undergoing specific types of cardiac surgery requiring cardiopulmonary bypass.

• Eligible surgeries include elective primary or re-operative coronary artery bypass graft and/or valvular and/or ascending aorta surgery.
• All eligible surgeries require cardiopulmonary bypass.
• Preoperatively, each patient's baseline physical, cognitive, and mental status is established.
• Ethical approval was obtained from the Swiss lead ethics committee (EKNZ 2022-01457) and Health Research Authority and Health and Care Research Wales, UK (REC 23/SW/0076).

The study is designed to address a gap in knowledge about the causes of neurological complications after cardiac surgery and effective neuroprotective strategies.

• The authors note that 'a lack of comprehensive knowledge about their causes and neuroprotective strategies has hindered the development of effective interventions to reduce these events.'
• The study aims to assess whether perioperative duration and magnitude of MAP deviation from an individual's CA limits are associated with adverse neurological complications.
• The study is registered on ClinicalTrials.gov as NCT05595954.