Accuracy of auditory evoked potential index in monitoring anesthetic depth during isoflurane anesthesia / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the accuracy of auditory evoked potential index (AAI) in monitoring the anesthetic depth during isoflurane anesthesia.Methods Thirty ASA Ⅰ or Ⅱ patients aged 18-55 years and undergoing elective surgery under general anesthesia were enrolled in this study. The patients were unpremedicated. Anesthesia was induced with midazolam 0.05 mg/kg, fentanyl 3 μg/kg and propofol 1 mg/kg. Tracheal intubation was facilitated with recuronium 0.1 mg/kg. The patients were mechanically ventilated (VT40 mm Hg. Anesthesia was maintained with isoflurane inhalation and intermittent intravenous boluses of vecuronium. Isoflurane was started with high-flow (FGF, 3 L/min) for 12 min followed by low-flow (LGF, 0.5 L/min). The inspired isoflurane concentration was set at 3%. The electrocardiogram (ECG), mean arterial pressure (MAP), heart rate (HR), pulse oxygen saturation (SpO2), end-tidal isoflurane concentration and AAI were continuously monitored during anesthesia and recorded before induction of anesthesia (baseline, To ), immediately after induction (T1), immediately before isoflurane inhalation (T2), at 3 min(T3), 6 min (T4), 9 min (T5) and 12 min (T6) during high-flow wash-in and at the end-tidal isoflurane concentrations of 0.8 MAC (T7), 1.0 MAC (T8) and 1.3 MAC (T9) during low-flow inhalation of isoflurane, respectively.Results AAI decreased gradually while the end-tidal isoflurane concentration increased during high-flow wash-in. And AAI was negatively correlated with the end-tidal isoflurane concentrations ( r = -0.896, P ＜ 0.01 ) during low-flow inhalation of isoflurane anesthesia.