Target control infusion: infusion for target effect site concentration

Anesthetic drugs are administered to provide a desired effect. There are va rious kinds of stimulation during surgery. Anesthesia management by using t arget control infusion will be a suitable apparatus for this management. Ho wever, there are no indexes for noxious stimuli of surgical procedure excep t for skin incision. In particular, the propofol concentration required for peritoneum incision, abdominal retractor or the interaction between propof ol and fentanyl have not yet been defined. We determined the concentrations by which 50% of patients did not respond somatically or hemodynamically at various surgical stimulations of skin incision, peritoneum incision, and a bdominal retraction after equilibration between blood and effect site of pr opofol and fentanyl. We also determined the awakening propofol concentratio ns obtained from infusion schema using abrupt discontinuation of propofol ( EC50) or a descending decrease in concentration to allow blood-effect site equilibration (EC50eq). Increasing fentanyl concentration markedly reduced the Cp50si, Cp50pi, and Cp50ret (p < 0.05), with 3 ng/ml fentanyl reducing the Cp50s from 62 to 77%. An analysis using multiple regression showed that blood pressure response was influenced mostly by the type of stimulation f ollowing by plasma fentanyl concentration, and somatic response. Propofol c oncentration does not significantly correlate with blood pressure response. The awakening concentration EC50eq of both groups was 2.2 mu g/ml regardle ss of anesthesia length.