Association of Processed Electroencephalography Derived Parameters with Postoperative Delirium in Patients with Parkinson's Disease Undergoing Elective Neurosurgery

Postoperative delirium is a multifactorial condition, with incidence ranging from 20% to 50%. Unfortunately, the implications of postoperative delirium extend beyond the immediate perioperative period. Bickel et al observed in their three-year follow-up that patients experiencing postoperative delirium (POD) exhibited cognitive decline and had an elevated risk of developing dementia compared to those without delirium after orthopedic surgeries.

Parkinson's disease is a neurodegenerative disorder that has been associated with an increased risk of developing delirium, with a prevalence rate of 34%. The incidence of postoperative delirium in this subset, reported after DBS in Parkinson's patients, ranges from approximately 22% to as high as ~43%. Patients with Parkinson's disease commonly undergo various elective surgical procedures, including deep brain stimulation (DBS) electrode insertion. The anesthetic management for DBS generally involves monitored anesthesia care with mild sedation, followed by patient awakening for microelectrode recording (MER) to ensure optimal electrode positioning. Increased propensity for postoperative delirium in these patients with Parkinson's has prompted foray into its predictive factors.

Intraoperative EEG has demonstrated significant promise as a predictor of postoperative delirium, especially in the elderly. A systematic review and meta-analysis by Likhvantsev et al found that the presence of burst suppression was associated with a 41% increase in the relative risk of POD, and the duration of burst suppression correlated with a higher occurrence of postoperative cognitive dysfunction (POCD). Presence and duration of burst suppression in the intraoperative period was found to be an independent predictor of postoperative delirium. In instances of delirium occurring in the absence of burst suppression, low absolute and relative frontal alpha power have been associated with its incidence.

Interestingly, all previous studies were conducted in patients without preexisting neurological conditions, with minimal literature focusing on intraoperative processed EEG in patients with Parkinson's. In an observational study by Astalosch et al, intraoperative burst suppression was found to be an influencer for the severity of delirium. There exists a significant gap in the evidence regarding the utility of intraoperative EEG-derived parameters in predicting the occurrence of delirium in Parkinson's disease.

Postoperative delirium, along with causing increased morbidity and longer hospital stay, could also lead to long-term effects, such as cognitive decline and increased vulnerability to dementia. And in patients with Parkinson's, due to consequence of delirium, there are reports higher mortality rate as compared to healthy individuals. Despite the recognized higher incidence of delirium and its effects in this patient population, there is a notable lack of research exploring intraoperative EEG-based predictors. This study aims to investigate the utility of presence of burst suppression, (along with various other processed EEG based parameters) as potential indicators of postoperative delirium in patients undergoing DBS. By exploring these factors, we hope to identify reliable markers of postoperative delirium that help us identify patients at risk, refine anesthetic techniques to minimize risk, ultimately enhance the quality of care provided to this particularly vulnerable set of patients.