Median effective target plasma concentration of remifentanil inhibiting responses to skull-pin placement when combined with propofol in female patients undergoing neurosurgery / 中华麻醉学杂志

ABSTRACT

Objective To determine the median effective target plasma concentration (EC50) of remifentanil inhibiting responses to skull-pin placement when combined with propofol in the female patients undergoing neurosurgery.Methods Sixteen female patients,aged 20-60 yr,with body mass index of 18-30 kg/m2,of American Society of Anesthesiologists physical status Ⅰ or Ⅱ,scheduled for elective neurosurgery under general anesthesia,were enrolled in this study.Anesthesia was induced with propofol and remifentanil given by target-controlled infusion and iv rocuronium 0.6 mg/kg.The target plasma concentration (Cp) of remifentanil and propofol was set at 5 ng/ml and 3 μg/ml,respectively.At 3 min after tracheal intubation,the target Cp of remifentanil was adjusted and set at 5 ng/ml in the first patient.The skull-pin was placed after the target effect-site and plasma concentrations were balanced.The Cp increased/decreased by 20％ each time in the next patient depending on whether or not the response to skull-pin placement was positive.The ratio between the two successive concentrations was 1.2.The response to skull-pin placement was defined as positive when heart rate and/or mean arterial pressure increased by 20％ of the baseline value within 1 min after placement.The EC50 and 95％ confidence interval of remifentanil required to inhibit responses to skull-pin placement were calculated when combined with propofol.Results The EC50 (95％ confidence interval) of remifentanil required to inhibit responses to skull-pin placement was 3.74 (3.43-4.09) ng/ml when combined with propofol.Conclusion When combined with propofol,the EC50 of remifentanil inhibiting responses to skull-pin placement is 3.74 ng/ml in the female patients undergoing neurosurgery.