This study will test whether using a Bispectral Index (BIS) monitor to guide sedation can reduce the amount of sedative medication given to adults in the intensive care unit (ICU) after cardiac surgery. BIS is a non-invasive, EEG-based monitor that shows a number from 0-100 to reflect level of consciousness. Researchers will compare BIS-guided sedation to standard sedation guided by clinical scales (such as the Richmond Agitation-Sedation Scale, RASS).

About 144 participants will be randomly assigned (1:1) to one of two groups at two hospitals in Austria (Medical University of Graz and Klinikum Wels-Grieskirchen). In the BIS group, clinicians will use BIS values and standard care to titrate sedation and will aim to avoid sustained BIS values below 50. In the control group, sedation will follow standard practices using clinical scales; BIS will be recorded but hidden from caregivers. The trial is open-label for treating staff; outcome assessors and data analysts will be blinded.

Participants will be in the study during their ICU sedation and mechanical ventilation period (typically more than 6 hours), with follow-up through ICU and hospital discharge. The primary outcome is the time-averaged dose of propofol (mg/kg/h) given during continuous ICU sedation until weaning (up to 72 hours). Secondary outcomes include duration of ventilation and sedation, depth of sedation measures, sedative and catecholamine doses, pulmonary infections (including ventilator-associated pneumonia), ICU and hospital length of stay, delirium, and in-hospital mortality.

Risks are minimal and may include mild skin irritation from forehead electrodes. Possible benefits include improved sedation management; benefits are not guaranteed. Taking part is voluntary.

Inclusion Criteria:

• Age ≥ 18 years
• Undergoing cardiac surgery with subsequent admission to the intensive care unit (e.g., valve surgery, coronary artery bypass grafting, aortic surgery)
• Planned or expected duration of invasive mechanical ventilation > 6 hours postoperatively
• Requirement for continuous sedation during ICU stay

Exclusion Criteria:

• Pre-existing neurological disorders affecting consciousness or sedation assessment (e.g., severe dementia, epileptic encephalopathy).
• Acute neurological events in the perioperative period (e.g., stroke, intracranial hemorrhage).
• Severe hepatic dysfunction (Child-Pugh Class C).
• Participation in another interventional study potentially affecting sedation or cognitive outcomes.
• Pregnancy or lactation.
• Do-not-intubate (DNI)/Do-not-resuscitate (DNR) orders or documented limitation of therapy.
• Patients in whom short-term survival is deemed unlikely due to the clinical course.

Types of data: De-identified individual participant data (IPD) underlying the primary and secondary outcomes (e.g., demographics, baseline characteristics, BIS values, sedation dosing, ventilation duration, ICU/hospital length of stay, delirium measures, adverse events).

Supporting documents: Study protocol, statistical analysis plan (SAP), data dictionary/metadata, and analytic code.

starting 12 months after publication of the primary results and for a period of 5 years thereafter

Available to qualified researchers with a methodologically sound proposal. Requests will be reviewed by the Principal investigator. Approved requestors must:

Sign a data use agreement (DUA) prohibiting re-identification and onward sharing.

Obtain local IRB/ethics approval (or exemption) for the proposed analysis. Use data solely for the approved purpose and comply with GDPR and applicable data protection laws.

Mode of access: Controlled access via the University Hospital Graz secure institutional repository. Instructions for requesting access will be provided via the study contact email: [selina.sartori@medunigraz.at]

Single-masked. Treating staff (care providers) are unblinded; outcome assessors (and data analysts) are blinded to group assignment. Participants are not specifically masked.