Effects of ovarian cycle on medlan-effecttve target plasma concentration of propofol TCI caused loss consciousness

Objective To evaluate the effects of ovarian cycle on median-effective target plasma concentration (EC50) of propofol administered by target controlled infusion (TCI) caused loss consciousness.Methods Forty ASA I or II patients who had age 20 - 39 (28.5 ± 4.8) years and were scheduled for elective gynecologic laparoscopic surgery were divided into 2 groups (n =20 each group) : The follicular phase group (F group, serum progesterone concentration O.31 1.52 ng/ml) and luteal phase group (L group, serum progesterone concentration 5.16 ～ 18.56 ng/ral).No premedication was administered.Propofol was administered by TCI.TCI system was incorporated with Marsh pharmacokinetic model.EC50 was determined by up-and-down sequential trial.The target phsma concentration (Cp) was set at 3.5 μg/ml in the fh-st patient in each group.Each time, Cp was increased/decreased by 10％ in the next patient depending on whether or not the loss consciousness occurred.Results The ECho and 95％ confidence interval of propofol TCI caused loss consciousness were 4.76 (4.52 -5.00) μg/ml in group F, 4.18(3.88 ～4.52)μg/ml in group L.EC50in group L was significantly lower than in group F (t =6.23, P ＜0.01).Conclusions As loss consciousness occurred, median-effective target plasma concentration of propofol in luteal phase was lower than that in follicular phase. Key words: Menstrual cycle;  Anesthesia, general;  Propofol/PK