A 40–year female has to undergo insicional hernia surgery under general anaesthesia. She complains of awareness during her past cesarean section. Which of the following monitoring techniques can be used to prevent such awareness ?

To quantify the level of sedation and anaesthesia objectively, the intuitive solution is to monitor the brain directly. The "bispectoral index (BIS)" monitor is the first quantitative electroencephalographic index used in clinical practice to assess the depth of anaesthesia.