不同剂量右美托咪定对病人七氟醚镇静最低肺泡有效浓度的影响

Effects of different doses of dexmedetomidine on minimum alveolar concentration of sevoflurane for seda- tion

目的探讨不同剂量右美托咪定对病人七氟醚镇静最低肺泡有效浓度（MAC）的影响。方法择期全麻下腹部手术病人，ASA分级I或Ⅱ级，年龄18—64岁，性别不限，采用随机数字表法分为4组：对照组（C组）和不同剂量右美托咪定组（D1组、D2组和D3组），D1组、D2组及功组分别静脉输注负荷量右美托咪定0．4、0．6、0．8μg／kg，经15min输注完毕，记录心血管不良反应的发生情况，继之分别以0．4、0．6、0．8μg·kg-1·h-1的速率静脉输注，c组静脉输注等容量生理盐水。负荷量输注完毕后，采用序贯法进行试验，通过调控挥发罐和氧流量使呼气末七氟醚浓度迅速达到目标浓度，C组、D1组、D2组及D3组起始呼气末七氟醚浓度分别为0．8％、0．7％、0．6％和0．5％，并维持此浓度15min，然后由观察者用中等音量的声音指令病人睁眼，出现睁眼反应，下一例病人七氟醚浓度升高1个浓度梯度，否则下一例病人降低1个浓度梯度，相邻浓度比值为0．9，将每次能够做出正确反应与不能够做出正确反应的中点为1个交叉点，直至每组出现第7个交叉点结束。计算七氟醚镇静MAC及其95％可信区间（CI）。结果功组心血管不良事件发生率明显高于D1.2组（P〈0．05）。C组、D1组、D2组及D3组七氟醚MAC及其95％CI分别为0．68％（0．64％～0．74％）、0．50％（0．47％～0．52％）、0．36％（0．32％～0．41％）和0．28％（0．26％-0．31％）。与c组比较，D1-3组七氟醚MAC降低（P〈0．05）；与D1组比较，D2组和D3组七氟醚MACe降低（P〈0．05）；与D2组比较，现组七氟醚MAC降低（P〈0．05）。结论右美托咪定0．6μg／kg既可明显降低病人七氟醚镇静MAC，又无不良反应发生，为适宜剂量。

Objective To investigate the effects of different doses of dexmedetomidine on the minimum al- veolar concentration （MAC） of sevoflurane for sedation in patients. Methods ASA physical status Ⅰ or Ⅱ pa- tients of both sexes, aged 18-64 yr, undergoing elective lower abdominal surgery performed under general anesthe- sia, were randomly divided into 4 groups： control group （group C） and different doses of dexmedetomidine groups （D1 , D2 and D3 groups） . In D1 , D2 and D3 groups, the loading dose of dexmedetomidine 0.4, 0.6 and 0.8 μg/ kg was intravenously infused over 15 min, respectively, adverse cardiovascular events were then recorded, followed by infusion at 0.4, 0.6 and 0. 8μg. kg- 1. h- 1 via a pump, respectively, while in group C, the equal volume of 0.9 % normal saline was given instead of dexmedetomidine. Sevoflurane administration was begun after completion of infusion of the loading dose. Up-and-down sequential allocation was used to determine the MAC. The initial end-tidal concentration of sevoflurane was set at 0.8% , 0.7% , 0.6% and 0.5% in C, D1 , D2 and D3 groups, respectively, and maintained at this level for 15 rain. Each time the concentration of sevoflurane increased/de- creased in the next patient depending on whether or not the patients correctly followed the verbal command to openhis eyes. The ratio between the two consecutive concentrations was 0.9. The middle point between the positive re- sponse and negative response served as a crossover pair. After at least 7 independent crossover pairs were observed in each group, the experiment was stopped. The MAC and 95 % confidence interval of sevoflurane were calculat- ed. Results The incidence of adverse cardiovascular events was significantly higher in D3 group than in D1 and D2 groups （ P 〈 0.05） .In C, D1 , D2 and D3 groups, the MAC （95% confidence interval） of sevoflurane was 0.68% （0.64%-0.74%）, 0.50% （0.47%-0.52%）, 0.36% （0.32%-0.41%） and 0.28%（0.26%-0.31%）, re- spectively. The MAC-awake of sevoflurane was significantly lower in D1-3 groups than in group C, in D2 and D3 groups than in group D1 , and in D3 group than in group D2 （ P 〈 0. 05）. Conclusion Dexmedetomidine 0. 6 μg/kg can significantly decrease the MAC of sevoflurane for sedation, induces no side effects and is the optimum dose in patients.