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

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