Association of sleep and anaesthesia EEG biomarkers with preoperative MoCA score: A pilot study

Introduction: Preoperative cognitive impairments increase the risk of postoperative complications. The electroencephalogram (EEG) could provide information on cognitive vulnerability. The feasibility and clinical relevance of sleep EEG (EEG(sleep)) compared to intraoperative EEG (EEG(intraop)) in cognitive risk stratification remains to be explored. We investigated similarities between EEG(sleep) and EEG(intraop) vis-a-vis preoperative cognitive impairments. Methods: Pilot study including 27 patients (63 year old [53.5, 70.0]) to whom Montreal cognitive assessment (MoCA) and EEG(sleep) were administered 1 day before a propofol-based general anaesthesia, in addition to EEG(intraop) acquisition from depthof-anaesthesia monitors. Sleep spindles on EEG(sleep) and intraoperative alpha-band power on EEG(intraop) were particularly explored. Results: In total, 11 (41%) patients had a MoCA <25 points. These patients had a significantly lower sleep spindle power on EEG(sleep) (25 vs. 40 mu v(2)/ Hz, p =.035) and had a weaker intraoperative alpha-band power on EEG(intraop) (85 vs. 150 mu v(2)/Hz, p =.001) compared to patients with normal MoCA. Correlation between sleep spindle and intraoperative alpha-band power was positive and significant (r = 0.544, p =.003). Conclusion: Preoperative cognitive impairment appears to be detectable by both EEG(sleep) and EEG(intraop). Preoperative sleep EEG to assess perioperative cognitive risk is feasible but more data are needed to demonstrate its benefit compared to intraoperative EEG.