Electroencephalographic Biomarkers, Cerebral Oximetry, and Postoperative Cognitive Function in Adult Noncardiac Surgical Patients: A Prospective Cohort Study

Abstract

Background Perioperative neurocognitive disorders are a major public health issue, though there are no validated neurophysiologic biomarkers that predict cognitive function after surgery. This study tested the hypothesis that preoperative posterior electroencephalographic alpha power, alpha frontal-parietal connectivity, and cerebral oximetry would each correlate with postoperative neurocognitive function. Methods This was a single-center, prospective, observational study of adult (>18 years old) male and female non-cardiac surgery patients. Whole-scalp, 16-channel electroencephalography and cerebral oximetry were recorded in the preoperative, intraoperative, and immediate postoperative settings. The primary outcome was the mean postoperative T-score of three NIH Toolbox Cognition tests – Flanker Inhibitory Control and Attention, List Sorting Working Memory, and Pattern Comparison Processing Speed. These tests were obtained at preoperative baseline and on the first two postoperative mornings. The lowest average score from the first two postoperative days was used for the primary analysis. Delirium was a secondary outcome (via 3-minute Confusion Assessment Method) measured in the postanesthesia care unit and twice daily for the first three postoperative days. Lastly, patient-reported outcomes related to cognition and overall well-being were collected three months post-discharge. Results Sixty-four participants were recruited with a median (interquartile range) age of 59 (48 – 66) years. After adjustment for baseline cognitive function scores, no significant partial correlation (ρ) was detected between postoperative cognition scores and preoperative relative posterior alpha power (%) (ρ, = -0.03, p=0.854), alpha frontal-parietal connectivity (via weight phase lag index) (ρ = -0.10, p=0.570, respectively), or preoperative cerebral oximetry (%) (ρ = 0.21, p=0.246). Only intraoperative frontal-parietal theta connectivity was associated with postoperative delirium (F(1,6,291)=4.53, p=0.034). No electroencephalographic or oximetry biomarkers were associated with cognitive or functional outcomes three months post-discharge. Conclusions Preoperative posterior alpha power, frontal-parietal connectivity, and cerebral oximetry were not associated with cognitive function after non-cardiac surgery.

Postoperative Delirium and the Older Adult: Untangling the Confusion

“…Preoperatively, these patients will show reduced beta and gamma power, and during transition to unconsciousness a reduced alpha power 35 . Other EEG patterns, such as intraoperative transition to theta activity, 36 presence of burst suppression, and specific emergence trajectories, can be used as predictive markers 37 . The effects of EEG-guided anesthesia and other anesthetic practices on POD remain a matter of debate but have shown promise (Table 1).…”

Guidelines on postoperative delirium

“…A few EEG-specific markers are associated with delirium, but research is still on-going. 2 We are not sure that the clinical data are strong enough to convince a majority of anaesthetists to make it standard clinical practice. In addition, the upper value of the 95% confidence interval for the comparison between processed EEG monitoring guidance and usual care is 1.01, suggesting that further studies might lead to statistical significance in the meta-analyses.…”