The Interaction between Remifentanil and Propofol during Total Intravenous Anesthesia and the Adequate Effect Site Concentration / 대한마취과학회지

ABSTRACT

BACKGROUND: This study was performed to evaluate the interaction between remifentanil and propofol by comparing median-effect concentration (EC50) of single and co-administration, and to find adequate combination doses for general anesthesia for gastrectomy. METHODS: Thirty-six ASA physical status 1 or 2 patients scheduled for gastrectomy were randomly assigned to the remifentanil, propofol, or combination group.To obtain the dose-effect curve of remifentanil or propofol only, the effect site concentration of each drug was escalated until bispectral index (BIS) was reached 40 by a target-controlled infusion (TCI) during the steady operational period.For the combination group, 0.25, 0.5, 1, 2, and 2.5 timed EC50 of each drug were co-administered.The heart rate, mean arterial pressure and BIS were measured during the study period.The interaction between remifentanil and propofol was analyzed with using isobologram. RESULTS: The EC50 of remifentanil for hypnosis (BIS 40) was 1.96 ng/ml, and that of propofol was 1.35microgram/ml.In the combination group, the EC50 of remifentanil was 0.81 ng/ml and that of propofol was 0.56microgram/ml.EC90 of remifentanil and propofol alone were 13.43 ng/ml and 4.88microgram/ml. For EC90 of the combination group, remifentanil 3.54 ng/ml and propofol 2.50 microgram/ml were required.The distance from the theoretical additive line in the isobologram was larger in the higher doses (EC50 < EC75 < EC90). CONCLUSIONS: This study shows that remifentanil and propofol reveal synergism by isobolographic analysis during intravenous anesthesia.