Effect of Ciprofol on Intraoperative Hypotension in Elderly Patients Receiving Renin-angiotensin System Inhibitors

Inclusion Criteria: 1. Patients undergoing elective abdominal surgery under general anesthesia 2. Duration of surgery exceeding 2 hours 3. Patients receiving long-term renin-angiotensin system inhibitor therapy (\>3 months prior to surgery) 4. Age ≥ 65 years 5. ASA classification II-III 6. Informed consent was obtained from patients or their guardians Exclusion Criteria: 1. History of allergy to opioids, propofol, or ciprofol components. 2. Anticipated difficult airway (limited mouth opening, restricted neck movement, or modified Mallampati grade III-IV) or difficult mask ventilation. Body mass index ≤18 or ≥35 kg/m². 3. Severe hepatic dysfunction (total bilirubin ≥3.0 mg/dL or AST/ALT ≥2 times the upper limit of normal). 4. Severe renal impairment (creatinine clearance ≤30 mL/min). 5. Cardiac diseases (AV block higher than first-degree, heart rate \<50 bpm, severe arrhythmias, severe valvular heart disease, heart failure, or unstable angina on the day of surgery). 6. Preoperative cognitive impairment, cerebrovascular disease, or history of psychiatric illness. 7. Abnormal thyroid-stimulating hormone levels or history of thyroid replacement therapy. 8. Unstable asthma or history of asthma. 9. Alcohol abuse, drug abuse, chronic opioid dependence, or analgesic use exceeding 3 months. 10. Lactating or pregnant women.