Sources, impacts, and mechanisms of non-pharmacological artifacts in processed electroencephalography monitoring during anaesthesia and intensive care: A scoping review

Background Processed EEG (pEEG) monitoring is widely used to assess depth of hypnosis during anaesthesia and sedation in intensive care. However, these systems are susceptible to non-brain-related artifacts. Although previous reviews have identified sources of artifacts, their specific effects on electroencephalographic signals and derived hypnotic indices have not been systematically synthesised. This scoping review aims to summarise non-pharmacological artifact sources affecting pEEG monitoring in perioperative and ICU settings, including their impact on hypnotic indices and underlying mechanisms. Methods A three-step search strategy was followed for this scoping review as detailed in a previously published protocol. Studies involving non-pharmacological, non–brain-related artifacts in human patients undergoing pEEG monitoring during anaesthesia or critical care were included. Databases searched were PubMed, Ovid MEDLINE, Embase, Cochrane Library, CINAHL, and Web of Science, alongside grey literature. Searches were conducted on 19 June and 11 November 2025. English-language articles or those with English translations were included. Screening and data extraction were performed using Covidence. Results Of 152 screened articles, 48 met inclusion criteria (31 case reports, 7 case series, 10 studies). pEEG Monitors included BIS (36 articles), Entropy (10), and SedLine (six). Thirty-one artifact types were identified: 13 were patient-derived and 18 were non–patient-derived. The most common artifacts were related to cardiac or neuromuscular activity. Thrity-seven articles reported artifacts falsely elevating hypnotic indices; 2 resulted in no change, and 2reported a decrease. Conclusions Processed EEG Hypnotic indices are vulnerable to a broad range of non-pharmacological artifacts from both patient and environmental sources. This review categorises these artifacts and summarises their effects and mechanisms, highlighting important limitations in interpreting pEEG data clinically.