Comparison of Narcotrend Index,Bispectral Index,spectral and entropy parameters during induction of propofol-remifentanil anaesthesia

OBJECTIVE: This study investigated the suitability of various electroencephalogram (EEG) parameters to describe anaesthetic drug effects in propofol-remifentanil anaesthesia. The investigated parameters were the Narcotrend Index (NI), the Bispectral Index (BIS), and standard spectral and entropy parameters. Additionally, it was investigated whether the effect of a fixed dosage of propofol on the attained depth of hypnosis during induction of anaesthesia is different in male and female patients. METHODS: Standardized inductions of anaesthesia in 10 male and 10 female patients (ASA status I or II, 15-75 years) were analysed. All patients received 4 mg propofol/kg over 6 min followed by 4 mg/kg/h. For analgesia, patients received 0.3 microg/kg/min remifentanil starting 2 min before propofol application. For EEG monitoring, the Narcotrend and the Aspect A-2,000 Bispectral Index monitor were used simultaneously. Data from start of propofol injection until 1 min after the end of the induction period (420 s) were used for statistical analysis. EEG parameters were evaluated every 10 s. RESULTS: The Narcotrend Index and the Bispectral Index had the highest mean correlations with the calculated propofol effect-site concentration and were able to distinguish stages from the awake state or the near awake state and stages of deep hypnosis. On the Narcotrend scale, more data points are available for levels of anaesthesia with relevance for maintenance of anaesthesia. The BIS values at the first occurrence of burst suppression were significantly higher than the corresponding NI values. During induction of anaesthesia, the same dosages of propofol (per kg body weight) given to men and women did not show different effects on the EEG. CONCLUSIONS: NI and BIS are superior to spectral and entropy parameters in describing changes of propofol concentration during induction of propofol-remifentanil anaesthesia.