Effect Of Different Target Concentrations Of Remifentanil On The EC50of Etomidate And In BIS In Female At Loss Of Conscioussness And Disappearance Of Painful Stimuli-induced Body Movement

Objective:Total intravenous anesthesia is need to combined use of multiple drugs, combination of anesthetics has the extremely vital significance on improving the quality of anesthesia, reducing the perioperative complications, declining the medical cost and ensuring the safety of patients. Mastering the interactions between drugs can avoid improper drug dosage, enhance the medicating security. But previous studies mainly focused on the interactions of opioid drugs and propofol, the studies about remifentanil and etomidate were relatively seldom. In this study,remifentanil and etomidate were both given by target-controlled infusion,the EC50s of etomidate infused with different concentrations of remifetanil and the BIS50s of patients at loss of consciousness and response to a standard electrical tetanic stimulation were determined. Comparing with propofol,we evaluated the dose-effect relationship and effect on BIS values of etomidate combined with common clinical concentration ranges of remifentanil.Methods:160AS A physical status I or II patients, aged18-65years for gynecology surgery were randomly assigned into two groups (n=80):groups of E and P,received etomidate and propofol by TCI respectively,then the group E were randomly divided into4groups (n=20):groups R0e,R1e,R2e and R3e which received remifentanil at a predict effect-site concentration of0,1,2and3ng/ml,and the group P were randomly divided into4groups (n=20):groups R0p,R1p,R2p and R3p which received remifentanil at different predict effect-site concentrations too. Anesthesia of group E was induced with remifentanil and etomidate both given by target-controlled infusion.Patients were received remifentanil at a predict effect-site concentration of0,1,2and3ng/ml(groupROe-R3e) firstly,then the TCI of etomidate was started at a predict plasma concentration of0.6μg/ml,and then increased by0.1μg/ml every1min until loss of consciousness and response of painful stimulus(groups Rle-R3e).In group P, the TCI of propofol was started at a predict plasma concentration of2μg/ml,and then increased by1μg/ml every1min,the rest of test was same as group E. Recording the plasma and effect-site concentrations of etomidate and the Bispectral index values at this two clinical end-points;MAP,HR and SPO2were also recorded.The50%effect predict plasma and effect-site concentrations of etomidate and effect BIS value in50%of the patients was determined by Probit method.Results:At the clinical end-point of loss of consciousness, the EC50s of etomidate in groups R0e-R3e were0.58μg/ml、0.54μg/ml、0.49μg/ml and0.39μg/ml respectively, the BIS50s were48、51、45、47. At the clinical end-point of loss response of painful stimulus, the EC50s of etomidate in groups Rle-R3e were1.06μg/ml、0.66μg/ml、0.46μg/ml and the BIS50s were54、49、50. At the clinical end-point of loss of consciousness, the EC50s of propofol in groups R0e-R3e were2.53μg/ml、2.38μg/ml、2.26μg/ml and1.92μg/ml respectively, the BIS50s were65、65、66and66. At the clinical end-point of loss response of painful stimulus, the EC50s of propofol in groups Rle-R3e were4.24μg/ml、2.81μg/ml and2.21μg/ml and the BIS50s were68.65and61.Conclusion:Remifentanil given by TCI at predict effet-site concentrations of1,2and3ng/ml produced a concentration-dependent decrease in the EC50of etomidate and propofol both at loss of consciousness and response of electrical tetanic stimulation,while had less effect on the BIS50. The BIS values of the group which recived target controlled infusion of etomidate group were significantly lower than propofol group both at loss of consciousness and resonse of painful stimulus.