The role and limitations of EEG ‐based depth of anaesthesia monitoring in theatres and intensive care

In this article we will look at some of the principles in processed EEG monitoring as applied to bispectral index (BIS). We outline why BIS should be regarded as a 'memory' monitor which in most circumstances reflects the depth of sedation or anaesthesia in particular patients. Its limitation in paralysed and non-paralysed patients must be understood in order for this monitor to be used safely. Finally, its emerging use in critical care will be explored.