Abstract:Objective To explore the appropriate initial dose of remimazolam for painless gastroenteroscopy in elderly patients based on bispectral index (BIS) monitoring. Methods A total of 165 elderly patients who underwent painless gastroenteroscopy at Linyi Traditional Chinese Medical Hospital from August to November 2022 were randomly divided into three groups: group A, group B, and group C, with 55 patients in each group. All the patients received intravenous injection of remifentanil 0.30 μg/kg at first. The initial dose of remimazolam in group A, B and C were 0.15 mg/kg, 0.20 mg/kg and 0.25 mg/kg, respectively. When the BIS＜75 or the modified observers assessment of alert / sedation score (MOAA/S) ＜3, gastroscopy was placed. Remifentanil 0.20 μg/kg was added before colonoscopy. The endoscopy〖LM〗 insertion time, interval time of first additional remimazolam, total time for gastroenteroscopy examination, total dosage of remimazolam for gastroenteroscopy examination, awakening time, and discharge time from recovery room in three groups were recorded. The following patients indexes ［including pulse oxygen saturation (SpO₂), heart rate (HR), mean arterial pressure (MAP), BIS values］ were recorded at five timepoints［before medication administration (T0), immediately after gastroscopy insertion (T1), the time of first additional remimazolam (T2), the end of gastroscopy (T3), and the end of colonoscopy (T4) ］, as well as the adverse reactions were observed during anesthesia and after surgery. Results Compared with group A, in group B and group C, the gastroscopy insertion time shortened (P＜0.05), the interval time of first additional remimazolam prolonged (P＜0.05) and the total remimazolam dosage increased (P＜0.05), the awakening time prolonged (P＜0.05), and in group C discharge time from recovery room prolonged (P＜0.05). Compared with group B, the total remimazolam dosage for gastroenteroscopy increased and discharge time from recovery room prolonged in group C (P＜0.05). In the three groups, compared with T0, HR increased at T1, BIS value and MAP decreased at T1-T4 (P＜0.05)； Compared with group A, the BIS value of group C decreased at T1 (P<0.05). There was no significant difference in SpO₂、 HR and MAP among the three groups at the same time (P＞0.05). The incidence of body movement or cough in groups B and C decreased (P＜0.05), and the incidence of hypoxemia in group C increased (P＜0.05). Conclusion Under BIS monitoring, in elderly patients with painless gastroenteroscopy, remimazolam initial dose of 0.20 mg/kg has a better sedative effect, shorter endoscopy insertion time, longer interval for the first additional remimazolam, earlier departure from the recovery room, less impact on respiratory and circulation, and fewer adverse reactions.