Electroencephalogram-based depth of anaesthesia measurement: Combining opioids with hypnotics

SummaryWithin the last few decades, the electroencephalogram has become a widely used tool for the automatic assessment of depth of anaesthesia. The method has, however, faced some significant challenges. One of these is that many different classes of anaesthetic drugs, all of which affect the electroencephalogram, are used nowadays simultaneously during operations. Especially, the assessment of depth of anaesthesia induced by combining opioids with hypnotics has been raised as one of the major problems in the field and a large body of literature dealing with this topic has been published. The problem is addressed in this review. After giving an overview of the electroencephalogram and derived computational parameters during anaesthesia, the paper focuses on presenting the relevant literature related to the depth of anaesthesia measurement during hypnotic–opioid anaesthesia. The main findings are summarized and suggestions for the electroencephalogram-based depth of anaesthesia assessment in the clinical environment as well as future research are given.