Effects of different target concentrations of remifentanil when combined with propofol on BIS in patients undergoing neurosurgery

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Objective To investigate the effects of different target concentrations of remifentanil when combined with propofol on BIS in patients undergoing neurosurgery. Methods Fifteen ASA Ⅰ or Ⅱ patients, aged 18-64 yr, weighing 50-85 kg, scheduled for intracranial surgery, were involved in this study. The patients received propofol by target controlled infusion (TCI) at a target effect site concentration (Ce) of 3μg/ml. TCI of remifentanil was started after TCI of propofol reached the preset Ce and Ce of remifentanil was increased step by step from 2 ng/ml to 3, 4, 5, 6, 7 and 8 ng/ml. Invasive BP, MAP, HR and BIS were continuously monitored and recorded when remifentanil reached the each preset Ce. Vecuronium 0.1 mg/kg was injected iv when Ce of remifentanil reached 5 ng/ml, and then the patients were intubated and mechanically ventilated 3 min later. The changes in BP, MAP, HR and BIS were recorded. When HR < 50 bpm and/or MAP < 60 mm Hg, TCI of remifentanil was stopped and iv atropine or ephedrine was given. Results BIS was significantly decreased after TCI of remifentanil when propofol reached 3 μg/ ml compared with the baseline value ( P < 0.05 or 0.01). BIS was significantly decreased when Ce of remifentanil ≥6 ng/ml compared with that when propofol reached 3 μg/ml ( P < 0.05 or 0.01) .Conclusion Low-concentration of remifentanil when combined with propofol has no effect on BIS, but when Ce of remifentanil≥ 6 ng/ml, BIS is obviously decreased. Key words: Piperidines; Propofol; Electroencephalography; Drug delivery systems