Background: Sedation is a cornerstone of management for mechanically ventilated patients in the intensive care unit (ICU). Achieving early target sedation while maintaining hemodynamic stability remains a major clinical challenge. Ciprofol, a novel intravenous sedative agent structurally derived from propofol, has shown promising efficacy and a potentially improved hemodynamic profile in preclinical and phase II/III studies. However, high-quality evidence from large, multicenter randomized trials in real-world ICU settings is lacking.

Objective: To evaluate the efficacy and safety of ciprofol versus propofol for sedation in mechanically ventilated ICU patients, as assessed by the incidence of early successful sedation without hypotension.

Methods: This is a multicenter, randomized, double-blind, parallel-group, active-controlled, noninferiority clinical trial conducted across 31 centers in China. A total of 366 patients will be randomized in a 1:1 ratio to receive either ciprofol or propofol. Eligible patients are adults (aged 18-80 years) admitted to the ICU receiving mechanical ventilation, with an expected sedation duration of 6-24 hours and a target Richmond Agitation-Sedation Scale (RASS) of +1 to -2. Key exclusion criteria include known allergy to ciprofol, BMI <18 or >30 kg/m², prior sedation for >3 days, severe cardiovascular, hepatic or renal dysfunction, Glasgow Coma Scale ≤12, expected survival ≤24 hours, pregnancy or lactation, and participation in other drug trials.

Patients will receive a loading dose (ciprofol 0.1 mg/kg or propofol 0.5 mg/kg) over 4 minutes, followed by a maintenance infusion titrated to achieve the target RASS. Remifentanil will be used for analgesia throughout. The primary composite outcome is successful sedation without hypotension within 30 minutes of study drug administration, defined as: (1) RASS within the target range of +1 to -2; (2) no use of rescue sedation; and (3) no occurrence of hypotension. Hypotension is defined as systolic blood pressure <90 mmHg, diastolic blood pressure <60 mmHg, mean arterial pressure <70 mmHg, or a >30% drop from baseline. Secondary outcomes include sedation success without hypotension at 1 hour, sedation without circulatory depression (hypotension or bradycardia) at 1 hour, drug utilization, duration of mechanical ventilation, extubation time, awakening time, delirium incidence (CAM-ICU), ICU length of stay, 28-day mortality, and safety profiles.

Based on an assumed 92% incidence in the ciprofol group versus 82% in the propofol group, with a two-sided alpha of 0.05 and 80% power, and allowing for a 5% dropout rate, the required sample size is 183 patients per group, totaling 366 patients. Analysis will be performed on the intention-to-treat population using logistic regression for the primary outcome, with results expressed as risk difference and relative risk with 95% confidence intervals.

Ethics and Dissemination: The study protocol has been approved by the ethics committee of the coordinating center and will be submitted to all participating sites. The trial is registered with ClinicalTrials.gov (NCT06538883). Results will be disseminated through peer-reviewed publications and academic presentations.

Keywords: Ciprofol, Propofol, Intensive care unit, Mechanical ventilation, Sedation, Hypotension, Randomized controlled trial

Inclusion criteria (patients who met all the following criteria):

1. Adults are sequentially admitted to ICU undergoing mechanical ventilation; Patients are expected to need 6-24 hours of sedation for the target RASS ranged from +1 to -2 after randomization;
2. Aged ≥ 18 and ≤ 80 years old, with no gender requirement;
3. The patients or their family members fully understood the objectives and significance of this study and voluntarily participated and signed informed consent forms.

Exclusion criteria (patients who met 1 of the following criteria were excluded):

1. Patients known to be allergic or contraindicated to ciprofol. 2. BMI<18 kg/m2 or >30 kg/m2. 3. Patients who had received sedation for more than 3 days in an ICU or in a general ward prior to being transferred to the ICU before signing an informed consent form.

4. Patients have the following medical history or evidence of any of the following conditions at screening, which may increase the sedation/anesthesia risk:

1. Cardiovascular system: New York Heart Association (NYHA) Class III and IV heart failure, Adams-stokes syndrome; patients who required vasopressor (equivalent norepinephrine ≥ 1μg/kg/min) to maintain a normal blood pressure.
2. Patients with hepatic and renal failure (liver function: refer to Child-Pugh grade C; renal function: eGFR ≤ 30 mL/(min·1.73 m2) [eGFR was calculated using the Modification of Diet in Renal Disease (MDRD) equation: eGFR = 175 × serum creatinine (SCr) - 1.234 × age - 0.179 × 0.79 (females)]; patients undergoing dialysis.
3. Patients with grand mal epilepsy and convulsion; a Glasgow coma scale (GCS) ≤ 12 points.

5. Patients with an expected survival of ≤ 24 h. 6. Pregnant or lactating females. 7. Patients participated in other drug clinical trials before screening. 8. Other conditions that patients were judged by the investigator to be unsuitable for inclusion in the study.