ciprofol is a recently introduced novel sedative drug. In comparison to the traditional propofol, ciprofol exhibits a higher affinity for GABA A receptors, approximately 4-5 times that of propofol, and possesses fewer side effects, particularly notable in respiratory depression and injection pain. In the context of general anesthesia induction, recent research has confirmed a 100% success rate in the induction of general anesthesia for elderly patients (65-80 years old) undergoing non-cardiac surgery with a dosage range of 0.2mg/kg-0.4mg/kg ciprofol. However, for elderly patients aged 65 and above, even up to 85 years old, it is currently not entirely clear what dosage should be selected for patients in different age groups. Consequently, we have designed this trial with the aim of exploring the dosage requirements of ciprofol during general anesthesia induction among elderly patients in various age brackets.

Methods: This is a prospective, non-controlled, non-randomized, single-blind study. Elderly patients aged 65 years and older were enrolled in the study with American Society of Anesthesiologists (ASA) physical status I or II undergoing general anesthesia. All patients were divided into five groups according to age, and the corresponding initial dose of ciprofol administered was selected according to the grouping, with subsequent doses of ciprofol determined according to the Dixon up-and-down method. At least seven crossover points were obtained before the conclusion of the study.The primary outcomes were the dose of ciprofol administered at the time of loss of consciousness (mg/Kg) and the plasma concentration of ciprofol.

After received the approvement of ethics committee of the Cancer Hospital of the University of Chinese Academy of Sciences (approval number IRB-2024-76(IIT)). The study was registered before patient enrollment in Clinicaltrials.Written informed consent was obtained from all participants. The study was performed from Jan 1, 2024 to Dec 31, 2025. 150 patients aged 65 years and above, ASA physical status I or II, undergoing surgery under general anesthesia and who were not allergic to the study drug were included in this study. Basic monitoring such as 3-lead electrocardiogram, pulse oximetry, and noninvasive blood pressure were arranged preoperatively. All patients were divided into five groups according to age, The initial dose of ciprofol for the first elderly patient was 0.2-0.4 mg/kg, the initial concentration was 0.4 mg/Kg for patients aged 65-74 years, 0.3 mg/Kg for patients aged 75-84 years, and 0.2 mg/Kg for patients aged 85 years or older, and the ciprofol doses for adjacent patients were set to be equidistantly spaced up and down by 0.05 mg/kg. Evaluation of the eyelash reflex and speech reflex was performed after intravenous infusion of ciprofol to observe whether LOC occurred within 4 min. After loss of consciousness, sufentanil (5ug/ml, diluted in 0.9% saline) and rocuronium bromide were given for endotracheal intubation.

Inclusion Criteria:

• 65 ≤ age years;
• ASA physical state I and II;
• Hadn't a history of allergy to the drugs used in this study;

Exclusion Criteria:

• America Society of Anesthesiologists (ASA) class >III;
• Allergic to anesthetic solutions or the drugs used in this study;
• Body mass index (BMI) ≤ 20 or ≥ 30 kg/m2;
• Using hypnotics, opioid analgesics, or anti-anxiety medications;
• Known or suspected heart failure (ejection fraction <40%), severe respiratory disease, renal or metabolic disease
• Refuse to participate or participate with other clinical investigators ;

Plan can be shared when required.