Remimazolam Versus Propofol for Maintenance of Anaesthesia During Major Hepatectomy Under Low Central Venous Pressure

The goal of this clinical trial is to learn whether remimazolam helps prevent low blood pressure better than propofol during major liver surgery in adults. All participants will have planned surgery to remove at least three liver segments. The main question is whether participants who receive remimazolam have less low blood pressure while the surgeon removes liver tissue. Researchers will measure both how low the blood pressure falls and how long it stays low. Researchers will randomly assign 224 participants to receive remimazolam or propofol to maintain general anesthesia. Participants will not know which drug they receive until their postoperative assessments are complete. The anesthesiologist giving the drug will know the assignment for safety reasons. Participants will: * Receive one of the two study drugs during surgery * Have their blood pressure monitored continuously * Receive standard treatment if their blood pressure becomes low * Complete follow-up through 30 days after surgery Researchers will also compare the use of medicines to support blood pressure, bleeding, blood transfusion, recovery after anesthesia, organ complications, heart injury, and adverse events.