A systematic review on the perioperative use of EEG as a predictor/diagnostic tool for postoperative delirium

Abstract Background The electroencephalogram (EEG) in the perioperative setting has been increasingly used as a tool for delirium prognostication and diagnosis. Delirium in the post‐operative setting occurs in 20‐25% of the patients aged 65 and older. The has been used for a long time in the intraoperative setting, with some measures being associated with the development of POD. Recently studies have been focusing on the use of the EEG preoperatively as a prediction tool, and postoperatively as a diagnostic tool for POD. Method We performed a systematic review to address the role of EEG in the perioperative setting as a tool for delirium prognosis and diagnosis. Twelve randomized control trials and twenty‐eight observational studies were identified. Result Common preoperative findings associated with the development of POD include: higher alpha power, increased alpha band connectivity but impaired structural connectivity, increased slow wave activity involving frontal and occipitoparietal cortex with accompanying break down in functional connectivity, lower EEG‐ asymmetry, lower values of pre‐operative spectral edge frequencies, and polysomnography findings of longer non‐REM stage 2 sleep. Common intraoperative findings associated with POD include: increased magnitude and duration of EEG suppression, reduced higher frequencies, increased prevalence and duration of BSR, and low BIS values. Finally, post‐operative findings associated with POD include: greater delta power while awake, alterations in delta in wake versus sleep state, and disruptions in connectivity. Conclusion The use of EEG as a diagnostic and prognostic tool has promising utility in the perioperative setting. In the pre‐and intraoperative setting, certain EEG markers may be utilized to predict delirium or triage which patients are at a higher risk of developing POD. Postoperatively, EEG use can predict and help diagnose POD. More studies are needed to further systematize and validate this data.