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目的:比较右美托咪定复合瑞芬太尼用于不同BMI患者结肠镜检查术的麻醉效力，以评价体质量因素对检查术疼痛程度影响的临床意义。方法:择期行结肠镜检查术患者，ASA分级Ⅰ或Ⅱ级，年龄18～64岁，依据BMI分为Ⅰ组(体质量过低组，BMI<18.5 kg/m 2)、Ⅱ组(体质量正常组，BMI 18.5～24.0 kg/m 2)和Ⅲ组(超重组，24.0 kg/m 2<BMI<30.0 kg/m 2)。各组患者2 min内静脉泵注规定剂量的右美托咪定，随后2 min内静脉泵注瑞芬太尼1 μg/kg并以0.1 μg·kg －1·min －1的速率维持至术毕，随即开始结肠镜检查术。采用上下序贯法，各组右美托咪定初始剂量均为0.3 μg/kg，相邻剂量比值为1.2；阳性反应定义为检查术中患者改良警觉/镇静评分>1分且发生体动，患者出现阳性反应时下一例选择高一级别的剂量；否则选择低一级别的剂量。采用Dixon-Massey公式计算右美托咪定半数有效剂量(ED 50)及95%可信区间( CI)。 结果:与Ⅰ组[0.42(0.38～0.47) μg/kg ]比较，Ⅱ组[0.23(0.19～0.27) μg/kg]和Ⅲ组[0.18(0.83～0.22) μg/kg]右美托咪定ED 50明显降低( P<0.05)；与Ⅱ组比较，Ⅲ组右美托咪定ED 50明显降低( P<0.05)。 结论:随着BMI升高，右美托咪定复合瑞芬太尼用于结肠镜检查术患者的麻醉效力明显增强，提示临床上应重视体质量因素对检查术疼痛程度的影响。

Objective:To compare the anesthetic potency of dexmedetomidine combined with remifentanil for colonoscopy in the patients with different body mass indexes (BMIs) to assess the clinical significance of the influence of weight on the level of pain during the procedure.Methods:American Society of Anesthesiologists Physical Status classification Ⅰ or Ⅱ patients, aged 18-64 yr, undergoing elective colonoscopy, were divided into 3 groups based on the BMI: group Ⅰ (underweight group, BMI<18.5 kg/m 2), group Ⅱ (normal weight group, BMI 18.5-24.0 kg/m 2), and group III (overweight group, 24.0 kg/m 2 < BMI <30.0 kg/m 2). The prescribed dose of dexmedetomidine was infused within 2 min, then remifentanil was infused as a bolus of 1 μg/kg within 2 min followed by an infusion of 0.1 μg · kg -1 · min -1 throughout the surgery, and then colonoscopy was performed in patients of each group. The up-and-down sequential allocation was used to determine the dose of dexmedetomidine, the initial dose of dexmedetomidine in each group was 0.3 μg/kg, and the ratio between the two successive doses was 1.2. The positive response was defined as the Modified Observer′s Assessment of Alertness/Sedation Scale score > 1 and occurrence of body movement during the operation. Each time the dose of dexmedetomidine increased/decreased in the next patient depending on whether or not the response was positive. The median effective dose (ED 50) and 95% confidence interval ( CI) of dexmedetomidine were calculated using the Dixon-Massey formula. Results:Compared with group Ⅰ (0.42 [95% CI 0.38-0.47] μg/kg), the ED 50 of dexmedetomidine was significantly decreased in group II (0.23 [95% CI 0.19-0.32] μg/kg) and in group III (0.18 [95% CI 0.13-0.22] μg/kg) ( P<0.05). The ED 50 of dexmedetomidine was significantly decreased in group Ⅲ when compared with group Ⅱ ( P<0.05). Conclusions:With the increase of patients′ BMIs, the anesthetic potency of dexmedetomidine for colonoscopy is significantly enhanced when combined with remifentanil, indicating that clinicians should pay attention to the influence of weight on the level of pain during procedures.