Effective doses of alfentanil combined with propofol for gastroscopy in patients of different ages under Narcotrend monitoring: a prospective dose-finding study utilizing the up-and-down sequential allocation method. - Jiang, Lili; Peng, Zhe; Deng, Yuhui; Qin, Zebang; Li, Jianxia; Huang, Jinping; Qin, Zaisheng (Perioperative Medicine, 2025)