目的:探讨间羟胺预防剖宫产术腰麻后低血压的量效关系。方法:行剖宫产术孕产妇100例，年龄18～40岁，单胎足月妊娠，孕周37～41n ＋6周，ASA分级Ⅰ或Ⅱ级，体重50～100 kg，身高150～170 cm。采用随机数字表法分为4组(n n＝25)：腰麻后分别静脉输注间羟胺0.25、1.00、1.75、2.50 μg·kgn -1·minn -1(D1组、D2组、D3组和D4组)。预防低血压有效的定义为从腰麻给药后至胎儿娩出期间无低血压(血压≤80%基础水平或≤90 mmHg)发生。采用Probit法计算间羟胺预防剖宫产术腰麻后低血压的半数有效剂量(EDn 50)和90%有效剂量(EDn 90)及其95%可信区间。记录腰麻后低血压、反应性高血压、心动过缓、恶心呕吐和寒战的发生情况。断脐即刻采集新生儿脐动脉血行血气分析，并记录新生儿出生后1 min时Apgar评分。n 结果:间羟胺预防剖宫产术腰麻后低血压的EDn 50及其95%可信区间为0.64 (0.14～0.95) μg·kgn -1·minn -1，EDn 90及其95%可信区间为2.00 (1.61～2.78) μg·kgn -1·minn -1。4组低血压和恶心呕吐发生率随间羟胺输注剂量的增加而降低(n P0.05)。n 结论:间羟胺预防剖宫产术腰麻后低血压的EDn 50和EDn 90分别为0.64和2.00 μg· kgn -1· minn -1。n “,”Objective:To determine the dose-effect relationship of metaraminol in preventing hypotension induced by spinal anesthesia in cesarean section.Methods:One hundred parturients undergoing elective cesarean section, aged 18-40 yr, who were at full term with a singleton fetus, at 37-41n + 6 weeks of gestation, of American Society of Anesthesiologists physical status Ⅰ or Ⅱ, weighing 50-100 kg, with height 150-170 cm, were allocated into 4 groups (n n = 25 each) using a random number table method: 0.25, 1.0, 1.75 and 2.5 μg·kg n -1·minn -1 metaraminol groups (D1, D2, D3 and D4 groups). Metaraminol 0.25, 1.0, 1.75 and 2.5 μg·kg n -1·minn -1 were intravenously infused after spinal anesthesia.Effective prevention of hypotension was defined as the absence of hypotension (blood pressure ≤80% of the baseline value or ≤90 mmHg) during the period from the end of administration of spinal anesthesia to the delivery of the fetus.The EDn 50, EDn 90 and 95% confidence interval of metaraminol in preventing hypotension induced by spinal anesthesia were calculated by Probit analysis.The development of hypotension, reactive hypertension, bradycardia, nausea and vomiting and shivering was recorded after spinal anesthesia.The umbilical arterial blood samples of neonates were collected immediately after cutting the cord for blood gas analysis.The Apgar scores of the neonates at 1 min after birth were recorded.n Results:The EDn 50 and 95% confidence interval of metaraminol in preventing hypotension induced by spinal anesthesia were 0.64 (0.14-0.95) μg·kg n -1·minn -1, and EDn 90 and 95% confidence interval were 2.00 (1.61-2.78) μg·kg n -1·minn -1.The incidence of hypotension and nausea and vomiting decreased with the increase in the dose of metaraminol infused in the four groups (n P0.05). There was no significant difference in the indexes of umbilical arterial blood gas analysis and Apgar score at 1 min after birth among the four groups (n P>0.05).n Conclusion:The EDn 50 and EDn 90 of metaraminol in preventing spinal anesthesia-induced hypotension are 0.64 and 2.00 μg·kg n -1·minn -1, respectively, in the patients undergoing cesarean section.n