Effects of different doses of dexmedetomidine on minimum alveolar concentration of sevoflurane required to inhibit the body movement evoked by skin incision / 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 required to inhibit the body movement evoked by skin incision.Methods ASA Ⅰ or Ⅱ patients of both sexes,aged 18-64 yr,with body mass index of 21-27 kg/m2,undegoing elective lower abdominal surgery under general anesthesia,were randomly divided into 4 groupscontrol group (group C) and different doses of dexmedetomidine groups (groups D1,D2 and D3 ).Dexmedetomidine 0.2,0.4 and 0.6 μg/kg in 15 ml of normal saline was infused over 30 min before induction of anesthesia in groups D1,D2 and D3 respectively.While 15 ml of normal saline was given instead in group C.Anesthesia was induced with inhalation of 8％ sevoflurane.The patients were mechanically ventilated after tracheal intubation.Anesthesia was maintained with inhalation of sevoflurane.The initial end-tidal concentration of sevoflurane was set at 3.0％,3.0％,2.5％,2.0％ in groups C,D1,D2 and D3 respectively.The ratio between the two successive concentrations was 0.9.Skin incision was made after 15 min of equilibratiton.At least 7 independent crossover pairs were observed in each group.The MAC of sevoflurane was the mean of the end-tidal concentration of sevoflurane of each crossover pair,and 95 ％ confidence interval (CI) was calculated.Results In groups C,D1,D2 and D3,18,20,20 and 22 patients were enrolled respectively.The MAC (95 ％ CI) of sevoflurane was 2.5 ％ (2.3 ％-2.8 ％ ),1.5 ％ ( 1.3 ％-1.7％),1.3％ (1.0％-1.6％) and 1.1％ (0.7％-1.5％) in groupsC,D1,D2 and D3 respectively.The MAC of sevoflurane was significantly lower in groups D1,D2,D3 than in group C,and in groups D2 and D3 than in group D1 ( P ＜ 0.05).There was no significant difference in the MAC of sevoflurane between groups D2 and D3 ( P ＞0.05).Conclusion Dexmedetomidine 0.2,0.4,0.6 μg/kg can significantly decrease the MAC of sevoflurane required to inhibit the body movement evoked by skin incision in a dose-dependent manner.