Determination of the 95% Effective Dose of Remifentanil for Moderate Sedation During Gastroscopy in Obese Patients

Introduction: Obesity increases the risk of hypoxemia during gastroscopy. The optimal remifentanil dose for effective and safe conscious sedation in this population remained unclear. Applying the biased coin design up-and-down sequential method, we aimed to determine the 95% Effective Dose (ED95) of remifentanil required for gastroscopy in obese patients. Materials and Methods: In this prospective interventional dose-finding study, patients aged 18-65 years with a BMI ≥ 30 kg/m2 (ASA class I-III) undergoing elective gastroscopy received remifentanil via target-controlled infusion. Patients with opioid allergy were excluded. A biased coin design-up-and-down method was used to determine the dosage, and the ED95 was estimated using isotonic regression. Ramsay sedation scores, Visual Analog Scale (VAS) pain scores, vital signs, and satisfaction ratings were recorded. Results: Forty-two patients were enrolled. Sedation was successful in 83.3% (35/42) of patients. The estimated ED95 of remifentanil was 0.915 μg/kg (95% CI: 0.790-0.989). The mean procedure time was 5.85 minutes. Hypoxemia occurred in 4.8% (n = 2, lowest SpO2 88%) and sinus bradycardia in 7.1% (n = 3). Patient and endoscopist satisfaction scores were 7.12 ± 1.42 and 6.75 ± 1.62, respectively. Discussion: This study found that remifentanil monotherapy can serve as an effective and safe strategy for conscious sedation in obese patients undergoing gastroscopy. We determined the effective dose ED95 to be 0.915 μg/kg (95% CI, 0.790-0.989), providing a potential evidence-based starting point for clinical practice. The favorable safety profile, characterized by a low incidence of hypoxemia, addressed a critical need for sedation strategies that minimize respiratory depression in this high-risk population. Future research should explore combinations with non-opioid adjuvants to further reduce opioid- related adverse effects and incorporate objective respiratory monitoring, such as capnography, to enhance safety assessment. Conclusion: Remifentanil monotherapy provided effective conscious sedation for gastroscopy in obese patients, showing a high success rate and low incidence of hypoxemia. The ED95 was determined to be 0.915 μg/kg.