Intraoperative Burst Suppression by Analysis of Raw Electroencephalogram Postoperative Delirium in Older Adults Undergoing Spine Surgery: A Retrospective Cohort Study.

Background: Postoperative delirium is a common complication in older adults, associated with poor outcomes, morbidity, mortality, and higher health care costs. Older age is a strong predictor of delirium. Intraoperative burst suppression on the electroencephalogram (EEG) has also been linked to postoperative delirium and poor neurocognitive outcomes.

Methods: In this a secondary analysis of data from the Perioperative Anesthesia Neurocognitive Disorder Assessment-Geriatric (PANDA-G) observational study, the raw EEGs of 239 spine surgery patients were evaluated. Associations between delirium and age, device-generated burst suppression ratio, and visual detection of the raw EEG were compared.

Results: Demographics and anesthesia durations were similar in patients with and without delirium. There was a higher incidence of burst suppression identified by analysis of the raw EEG in the delirium group than in the no delirium group (73.45% vs. 50.9%; P=0.001) which appeared to be driven largely by a higher incidence of burst suppression during maintenance of anesthesia (67.2% vs. 46.3%; P=0.004). Burst suppression was more strongly associated with delirium than with age; estimated linear regression coefficient for burst suppression 0.182 (SE: 0.057; P=0.002) and for age 0.009 (SE: 0.005; P=0.082). There was no significant interaction between burst suppression and age (-0.512; SE: 0.390; P=0.190). Compared with visual detection of burst suppression, the burst suppression ratio overestimated burst suppression at low values, and underestimated burst suppression at high values.

Conclusion: Intraoperative burst suppression identified by visual analysis of the EEG was more strongly associated with delirium than age in older adults undergoing spine surgery. Further research is needed to determine the clinical importance of these findings.