Objective:To investigate the effect of acute hypervolemic hemodilution (AHH) with 6% hydroxyethyl starch 130/0.4 on pharmacodynamics of propofol during successful laryngeal mask airway (LMA) implantation.Methods:American Society of Anesthesiology physical status Ⅰ or Ⅱ patients, aged 30-60 yr, with body mass index of 18.5-25.0 kg/m 2, undergoing elective extensive total hysterectomy under general anesthesia, were divided into 2 groups: AHH group (group A) and control group (group C). In group A, 6% hydroxyethyl starch 130/0.4 was infused at a rate of 20 ml/min for AHH, and the target hematocrit was 30%.In group C, lactated Ringer′s solution was infused according to the " 4-2-1" rule to supplement physiological requirements, and anesthesia induction was performed after 10 min of stabilization.Sufentanil was administered by target-controlled infusion using Bovil pharmacokinetic model with effect-site concentration (Ce) of 0.25 ng/ml, 3 min later propofol was given by target-controlled infusion using Schnider model.The Ce of propofol in the first patient was set at 5.0 μg/ml.Each time the concentration of propofol was increased/decreased by 0.5 μg/ml according to the sequential method.LMA was inserted following 1 min equilibration between plasma concentration and Ce of propofol.The trial was terminated when 8 consecutive inflection points of failed/successful LMA insertion occurred.The EC 5, EC 50, EC 95 and 95% confidence interval (95% CI) of propofol were calculated by probit regression analysis. Results:In group A, the EC 5 (95% CI), EC 50 (95% CI) and EC 95 (95% CI) of propofol when LMA was successfully placed were 4.237 (3.090-4.514) μg/ml, 4.802 (4.500-5.078) μg/ml and 5.443 (5.125-7.304) μg/ml, respectively.In group C, the EC 5 (95% CI), EC 50 (95% CI) and EC 95 (95% CI) of propofol when LMA was successfully placed were 2.408 (1.190-2.756) μg/ml, 3.120 (2.690-3.472) μg/ml and 4.042 (3.582-7.431) μg/ml, respectively.There was significant difference in EC 5, EC 50 and EC 95 between the two groups ( P<0.01). Conclusion:AHH with 6% hydroxyethyl starch 130/0.4 can decrease the efficacy of propofol when LMA is successfully implanted.