Effects of different doses of dexmedetomidine on minimum alveolar concentration of sevoflurane for sedation / 中华麻醉学杂志

ABSTRACT

Objective To investigate the effects of different doses of dexmedetomidine on the minimum alveolar concentration (MAC) of sevoflurane for sedation in patients.Methods ASA physical status Ⅰ or Ⅱ patients of both sexes,aged 18-64 yr,undergoing elective lower abdominal surgery performed under general anesthesia,were randomly divided into 4 groupscontrol 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 0.8 μg· 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 min.Each time the concentration of sevoflurane increased/decreased in the next patient depending on whether or not the patients correctly followed the verbal command to open his eyes.The ratio between the two consecutive concentrations was 0.9.The middle point between the positive response 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 calculated.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％),respectively.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 0.6μg/kg can significantly decrease the MAC of sevoflurane for sedation,induces no side effects and is the optimum dose in patients.