Abstract: AIM: To determine the median effective plasma concentration (Cp50) of propofol inhibiting body movement when combined with butorphanol in patients undergoing hysteroscopic surgery. METHODS: Twenty-one patients scheduled for elective hysteroscopic surgery under non-intubated intravenous anesthesia, age 20-55 years old, ASA physical status Ⅰ or Ⅱ, were enrolled in this study, and anesthesia was induced by target-controlled infusion of propofol. Hysteroscopy was performed only when the plasma concentration and the concentration of the effector chamber were balanced. Butorphanol 20 μg/kg was injected intravenously at 5 min before surgery. The depth of anesthesia and adverse reactions during anesthesia was monitored. The plasma target concentration (Cp) of propofol was determined by up-and-down method, the first patient was 2.5 μg/mL, each time Cp increased/decreased by 10% in the next patient depending on whether or not body movement occurred. The patients were divided into positive and negative groups according to the results. The Cp50 and 95% confidence inlerval (CI) of propofol inhibiting body movement were calculated by up-and-down formula when combined with butorphanol in patients undergoing hysteroscopic surgery. RESULTS: The Cp50(95%CI) of propofol required to inhibit body movement was 2.23(2.12-2.34) μg/mL when combined with butorphanol in patients undergoing hysteroscopic surgery. None of the patients had serious adverse reactions. CONCLUSION: The Cp50 of propofol required to inhibit body movement is 2.23 μg/mL when combined with 20 μg/kg butorphanol in patients undergoing hysteroscopic surgery. It provides a reference for safe dosage of anesthesia in hysteroscopic surgery.

Key words: propofol, butorphanol, hysteroscopic surgery, median effective plasma concentration