The Effect of Remimazolam Tosylate on the Incidence of Postoperative Delirium in Older Patients Undergoing Cardiac Surgery: A Prospective Randomized Controlled Trial

Inclusion Criteria 1\. Age ≥65 years. 2. Undergoing elective cardiac surgery with cardiopulmonary bypass, including coronary artery bypass grafting (CABG), valve surgery, or combined CABG and valve surgery. 3\. Admission to the cardiac surgery intensive care unit (ICU) after surgery, with an anticipated need for invasive mechanical ventilation and continuous sedation for at least 2 hours. 4\. Written informed consent obtained from the participant or their legally authorized representative. 5\. No delirium identified during the preoperative assessment. Exclusion Criteria 1. Emergency or salvage cardiac surgery. 2. Heart transplantation, ventricular assist device implantation, surgery for aortic dissection requiring deep hypothermic circulatory arrest, or other cardiac procedures outside the scope of this study. 3. Severe psychiatric disorders, diagnosed Alzheimer's disease or dementia, or preoperative delirium. 4. Severe alcohol use disorder or a history of severe alcohol misuse. 5. Previous cerebrovascular events or other conditions causing severe visual, hearing, or communication impairment that would prevent reliable delirium assessment despite appropriate assistance. 6. Known hypersensitivity or contraindications to either study drug or its excipients, or severe hepatic or renal failure. 7. Decompensated acute circulatory failure or hemodynamic instability at the time of randomization. 8. Concurrent participation in another interventional clinical trial that could affect the primary outcome.