Dexmedetomidine Pretreatment Reduces Predicted Effect-site Concentration Of Propofol Required For Loss Of Consciousness And Laryngeal Mask Airway Insertion

Objective:To investigate the effect of dexmedetomidine on the predicted effect-site concentration of propofol required for loss of consciousness (LOC) and Laryngeal Mask Airway(LMA) insertion.Methods:40ASA physical status1and2men, age between18-65-year old, BMI15-30, scheduled for minor urological procedures. Patients were randomly allocated to a dexmedetomidine group or a control group. Ten minutes before propofol TCI induction, dexmedetomidine group patients received dexmedetomidine lug/kg, while control group patients received saline. Propofol was given in a target-controlled infusion and target blood concentration was gradually increased until LOC. The effect-site concentrations for attempting LMA insertion was predetermined by modifying Dixon’s up and down method. LMA insertion was attempted without muscular blocking agents.Results:The effect-site concentration of propofol required for LOC was2.28±0.12ug/ml for the control group and1.03±0.19ug/ml for the dexmedetomidine group(P<0.05). The predicted effect-site concentration of propofol alone at which50%of patients succeeded in LMA insertion (EC50LMI) was4.09ug/ml (95%CI:3.68-4.59ug/ml). Pretreatment with dexmedetomidine lug/kg decreased EC50LMI to2.85ug/ml (95%CI:2.52-3.19ug/ml).Conclusion:Pretreatment with dexmedetomidine1ug/kg reduced the propofol concentration required for both LOC (45%) and LMA insertion (30%) in men.