Abstract: Objective To observe the anesthetic effect of different doses of remifentanil combined with dexmedetomidine in the treatment of uterine leiomyomas by high intensity focused ultrasound(Hifu knife).Methods A total of 90 patients who were scheduled for uterine fibroid embolization by Hifu knife were selected. According to the doses of remifentanil for anesthesia maintenance, the patients were divided into three groups: a low-dose remifentanil group(group L) at 0.06 μg/(kg·min), a middle-dose remifentanil group(group M) at 0.08 μg/(kg·min), and a high-dose remifentanil group(group H) at 0.1 μg/(kg·min). The three groups were compared for their mean arterial pressure(MBP), heart rate(HR), pulse oxygen saturation(SpO₂) and Ramsay sedation scores immediately before anesthesia(T1), immediately before the end of dexmedetomidine pumping(T2), at the beginning of surgery(T3), 10 min after the surgery started(T4) and 10 min after the surgery finished(T5). In addition, the number of cases requiring additional analgesics and the number of adverse reactions such as hypoxia, bradycardia and hypotension were recorded.Results At T4, group H had slower HR and less SpO₂ than group L and group M(P＜0.05). At T3 and T4, the difference of Ramsay sedation scores among the three groups was statistically significant. The number of cases requiring additional remifentanil in group L was significantly more than those in group M and group H. The incidence of intraoperative hypoxia in group H was significantly higher than those in group L and group M.Conclusions Remifentanil combined with dexmedetomidine can meet the needs for the treatment of uterine leiomyomas by Haifu knife. After pumping a loading dose of dexmedetomidine, an initial pumping dose of remifentanil at 0.08 μg/(kg·min) is the optimal.