Effects Of Different Loading Doses Of Dexmedetomidine On Bispectral Index Under Stepwise Propofol Target Controlled Infusion

Purpose:Stepwise propofol target controlled infusion (TCI) can achieve a less disturbed condition of hemodynamics and respiration. Its combination with dexmedetomidine may have some advantages for patients. We studied the effects of different loading doses of dexmedetomidine on Bispectral Index (BIS) under stepwise propofol TCI.Methods:Forty patients were randomly assigned into Group D1.0,D0.5,D0.25and D0, in which dexmedetomidine1.0,0.5,0.25or0?g·kg-1was infused over10min followed by0.5?g·kg-1·h-1and stepwise propofol TCI, which was administered with target effect site concentration (Ce) at0.5?g·mL-1, and increased until2.5?g·mL-1by1.0?g·mL-1after5min reaching target Ce. BIS, HR, MAP, SPO2, RR and ETCO2were recorded before loading dose (T0), at5min (T5min) and10min (T10min) after starting infusion, after5min reaching Ce of0.5,1.5and2.5?g·mL-1(Tp0.5, Tp1.5and Tp2.5).Results:BIS values in Group D1.0were significantly lower compared with those in Group Do since T10min and those in Group D0.5and D0.25since Tp0.5. IN Group D1.0, HR decreased significantly at T5min and Tiomin, HR at T10min was significantly lower compared with that in Group Do. MAP kept stable during the loading doses infusion and decreased to some degree after propofol infusion in all groups. Changes in SPO2, RR and ETCO2were similar among the groups without respiration depression.Conclusion:Loading dose of dexmedetomidine1.0?g·kg-1, not0.5?g·kg-1or less, over10min followed by0.5?g·kg-1·h-1can definitely decrease BIS under stepwise propofol TCI with clinically stable blood pressure and without respiration depression, while attention should be paid to decreased heart rate.