Processed EEG from depth of anaesthesia monitors and seizures: A scoping review.

Purpose: Processed electroencephalogram (EEG) is used peri-operatively for monitoring depth of anaesthesia. Because these utilise EEG data, attempts have been made to investigate their use in diagnosing and monitoring seizures. This is important as formal EEG monitoring can be hard to obtain in many critical care environments. We undertook a scoping review of the evidence for using processed EEG (pEEG) from depth of anaesthesia monitors for this indication.

Methods: Medline, Psych INFO, and Embase were searched for peer-reviewed journals until 20 March 2021. Data and conclusions taken from the study of pEEG in both critical care and peri-operative settings have been included in a qualitative synthesis about the current evidence for the use of pEEG in the detection and monitoring of seizures.

Results: Searches yielded 8 observational studies, 1 randomised trial and 15 case reports in which the use of pEEG in critical care and peri-operative medicine was described. Most concerned the Bispectral Index (BIS) device. The majority of observational studies reported the use of BIS for optimisation of burst suppression in patients with refractory status-epilepticus (RSE), or in the comparison of pEEG data with conventional EEG during epileptic activity. Multiple case reports describe the application of pEEG in the presence of disorders of consciousness as a tool for detection of non-convulsive status-epilepticus, finding variable trends in the pEEG output.

Conclusions: Processed EEG may be helpful in monitoring pharmacologically induced burst suppression. Despite this, its use in the diagnosing or monitoring seizure activity is controversial and currently not evidenced, with numerous confounding variables that requires systematic assessment in future studies.