The Effect Of Dexmedetomidine On The Effective Concentration Of Propofol Target-controlled Infusion For Unconsciousness

Objective To evaluate the effect of the different dose of dexmedetomidine on the effective concentration and the BIS of propofol target-controlled infusion (TCI) for unconsciousness.Methods One hundred patients(ASA Ⅰ～Ⅱ) scheduled for elective operation under general anesthesia were enrolled in this study. All patients were randomly divided into five groups(n=20):dexmedetomidine group Ⅰ (group D1), dexmedetomidine group Ⅱ (group D2), dexmedetomidine group Ⅲ(group D3), dexmedetomidine group IV (group D4) and control group (group C). In group D1, group D2, group D3and group D4,0.25μg/kg,0.5μg/kg,0.75μg/kg and1.0μg/kg of the doses dexmedetomidine was administered intravenously by micro pump respectively for over10minutes before general anesthetic induction, while in group C, same volume of0.9%normal saline was given by the same way. Propofol was used to anesthetic induction by targetcontrolled infusion (TCI),1.2μg/ml was set as start target plasma concentration, then0.3μg/ml was increased every30seconds until the patients eyelashreflex disappearing and doing no respond to verbal instructions. Sulfentanil and Cis-atracurium were administered intravenously, and pure oxygen was inhaled before endotracheal intubation was enforced. The parameters of MAP and HR were recorded before dexmedetomidine or0.9%normal saline infused intravenously (TO),10min after intravenous infusion (T1), the time that patients eyelashreflex disappeared and did no respond to verbal instructions (T2), preintubation(T3),1min after intubation (T4),3min after intubation(T5),5min(T6) after intubation. The target effect-site concentration and BIS of propofol for unconsciousness in group Dl, D2, D3, D4and C was computed and compared.Results At T2, The target effect-site concentration of propofol for unconsciousness in group D1, D2, D3and D4was lower than in group C (P<0.01). BIS in group D2, D3and D4was lower than in group C (P<0.05). In group C, HR and MAP after the intubation was significantly greater than before (P<0.05), however, in group D showed no change (P>0.05); HR and MAP in group D was lower than in group C at T4(P <0.05).Conclusion With the increase of the dose of dexmedetomidine, the effective concentration of propofol at loss of consciousness decreased and the BIS is higer at loss of consciousness than without dexmedetomidine; Dexmedetomidine reduces the response of endotracheal intubation.