This prospective, randomized, comparative study aims to compare the efficacy and safety of three different doses of remimazolam (0.2 mg/kg, 0.3 mg/kg, and 0.4 mg/kg) combined with sufentanil and propofol for painless gastroscopy in pediatric patients. The study will assess sedation quality, propofol consumption, hemodynamic stability, and adverse event profiles to identify an optimal remimazolam dosing regimen.

Pediatric patients undergoing gastrointestinal endoscopy often require deep sedation. Propofol is commonly used but can cause injection pain, respiratory depression, and hemodynamic instability. Remimazolam, a novel ultra-short-acting benzodiazepine, offers rapid onset, predictable recovery, and potentially better hemodynamic stability. This study investigates three doses of remimazolam (0.2 mg/kg, 0.3 mg/kg, and 0.4 mg/kg) co-administered with sufentanil (0.1 µg/kg) and titrated propofol to achieve a Modified Observer's Assessment of Alertness/Sedation (MOAA/S) score ≤ 2 in 180 pediatric patients (ASA I-II, aged <18 years) undergoing gastroscopy. Patients are randomly assigned to one of three remimazolam dose groups. The study will evaluate total propofol dosage, hemodynamic changes (blood pressure, heart rate), time to sedation, awakening and recovery times, incidence of adverse events (e.g., hypotension, respiratory depression, injection pain), and satisfaction scores. The goal is to determine a remimazolam dose that provides effective sedation with reduced propofol requirements and an improved safety profile.

Inclusion Criteria:

• Patients scheduled for elective gastrointestinal endoscopy under anesthesia.
• Patients classified as American Society of Anesthesiologists (ASA) physical status I or II.
• Patients aged 3 to under 18 years of age.
• Written informed consent provided by parents or legal guardians.

Exclusion Criteria:

• Patients with known or suspected difficult airway, severe systemic disease (ASA ≥ III).
• Uncorrected significant abnormal liver or kidney function that could significantly alter drug metabolism (e.g., AST/ALT > 2x upper limit of normal, eGFR < 30 mL/min/1.73m²).
• Known allergy to study medications (remimazolam, propofol, sufentanil, or their components including egg or soy for propofol).
• Congenital illnesses such as severe congenital heart disease, or other conditions that may impact treatment observation or increase anesthetic risk.
• Patients who were obese (defined as BMI > 95th percentile for age and sex) or severely malnourished (BMI < 3rd percentile for age and sex).
• Patients who had taken sedatives, opioid analgesics (other than prescribed for chronic pain), or psychotropic medications (e.g., antidepressants, antipsychotics) within 24 hours prior to the procedure (unless part of their regular, stable medication regimen for a chronic condition, as assessed and deemed safe by the anesthesiologist).
• Patients with pre-existing severe, uncontrolled mental illness or significant cognitive dysfunction that would preclude assessment of sedation or cooperation.
• Patients who had participated in other clinical trials within the past 4 weeks.
• Contraindications to the planned endoscopic procedure (e.g., recent gastrointestinal perforation, bowel obstruction).