This study is a non-interventional, observational research project focused on monitoring sedation levels in patients who have undergone cardiac surgery. It uses a tool called Bispectral Index (BIS), which measures brain activity to assess sedation depth. The goal is to understand how often patients experience deep sedation (BIS <50) during the first 48 hours in the ICU and to explore its impact on clinical outcomes like ventilation duration, ICU stay length, and complications such as infections or delirium.

The study is conducted at two hospitals in Austria and involves patients who require mechanical ventilation and continuous sedation for more than six hours after surgery. BIS data will be collected continuously, but the readings will be blinded to the clinical team, meaning they will not influence patient care. Sedation will be managed using standard clinical practices.

The findings aim to improve sedation management in ICUs.

Inclusion Criteria:

• Age ≥ 18 years.
• Undergoing cardiac surgery with subsequent admission to the ICU
• expected duration of invasive mechanical ventilation > 6 hours postop.
• Written informed consent obtained from the patient or legal representative (if the patient is not capable of consent).

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.
• Patients in whom short-term survival is deemed unlikely due to clinical course

patients admitted to the ICU following cardiac surgery. These patients are expected to require invasive mechanical ventilation and continuous sedation for more than 6 hours postoperatively.