Effect of dexmedetomidine on the EC50 of propofol target-controlled infusion for respiratory depression

Objective To determine the effect of systemic dexmedetomidine on the median effective concentration (EC50)of propofol target-controlled infusion (TCI)for respiratory depression. Methods Forty-nine ASA Ⅰor Ⅱpatients,scheduled for elective surgery were randomly allocated to receive dexmedetomidine (group D) and sodium chloride (group C).Twenty-five patients in group D received intravenous infusion of 0.4 μg/kg dexmedetomidine and twenty-four patients in group C received intravenous infusion of 5 ml normal saline for 5 minutes. 10 minutes later propofol TCI was administrated. BIS,HR,SBP,DBP,ECG,VT,MV,PETCO2,RR,SpO2 and OAA/S were recorded before drug anesthesia (T1),1min(T2),5 min(T3) and 10 min(T4)after dexmedetomidine infusion and 1min(T5),5 min(T6) after propofol TCI and termination of the study(T7). The EC50 and confidence interval was calculated.Results EC50 of propofol TCI for respiratory depression was 2.35 μg/ml (95% confidence interval was 2.31-2.39 μg/ml) in group D and 2.62 μg/ml (95% confidence interval was 2.51-2.72 μg/ml) in group C. The EC50 of propofol TCI for respiratory depression in group D was lower than that in group C(P0.05). The BIS values and OAA/S for patients in group D were lower than those in group C(P0.05).Conclusion 0.4 μg/kg dexmedetomidine administration before propofol target-controlled infusion could decrease the propofol EC50 for respiratory depression,and increase the depth of sedation.