Age-Related EEG Features of Bursting Activity During Anesthetic-Induced Burst Suppression

Abstract

Electroencephalographic (EEG) Burst Suppression (BSUPP) is a discontinuous pattern characterized by episodes of low voltage disrupted by bursts of cortical synaptic activity. It can occur while delivering high-dose anesthesia. Current research suggests an association between BSUPP and the occurrence of postoperative delirium in the post-anesthesia care unit (PACU) and beyond. We investigated burst micro-architecture to further understand how age influences the neurophysiology of this pharmacologically-induced state. We analyzed a subset of EEG recordings (n = 102) taken from a larger data set previously published. We selected the initial burst that followed a visually identified “silent second,” i.e., at least 1 s of iso-electricity of the EEG during propofol induction. We derived the (normalized) power spectral density [(n)PSD], the alpha band power, the maximum amplitude, the maximum slope of the EEG as well as the permutation entropy (PeEn) for the first 1.5 s of the initial burst of each patient. In the old patients >65 years, we observed significantly lower (p < 0.001) EEG power in the 1–15 Hz range. In general, their EEG contained a significantly higher amount of faster oscillations (>15 Hz). Alpha band power (p < 0.001), EEG amplitude (p = 0.001), and maximum EEG slope (p = 0.045) all significantly decreased with age, whereas PeEn increased (p = 0.008). Hence, we can describe an age-related change in features during EEG burst suppression. Sub-group analysis revealed no change in results based on pre-medication. These EEG changes add knowledge to the impact of age on cortical synaptic activity. In addition to a reduction in EEG amplitude, age-associated burst features can complicate the identification of excessive anesthetic administration in patients under general anesthesia. Knowledge of these neurophysiologic changes may not only improve anesthesia care through improved detection of burst suppression but might also provide insight into changes in neuronal network organization in patients at risk for age-related neurocognitive problems.

Electroencephalogram-Based Complexity Measures as Predictors of Post-operative Neurocognitive Dysfunction

“…We accounted for advances in clinical anesthesiology practice by selecting and analyzing EEG epochs that were free of artifacts, adjunct anesthetic drug exposure, and burst suppression. Intraoperative burst suppression has been associated with postoperative delirium in prior studies ( Soehle et al, 2015 ; Kratzer et al, 2020 ; Pedemonte et al, 2020 ; Shao et al, 2020 ), yet modest reductions in burst suppression have not been shown to reduce postoperative delirium incidence ( Wildes et al, 2019 ; Tang et al, 2020 ). Our data raise the possibility that EEG metrics that are present even in the absence of burst suppression may be associated with post-operative neurocognitive outcomes, similar to our prior finding that lower intraoperative alpha power is associated with lower preoperative cognitive function ( Giattino et al, 2017 ).…”

“…While most prior research on EEG as a predictor of delirium has predominantly relied on analysis of EEG data collected either intra-operatively ( Kratzer et al, 2020 ; Sun et al, 2020 ) or pre-operatively ( van Montfort et al, 2020 ), here we compared the pre-operative and intra-operative EEG signals. We observed relative changes in EEG complexity from before to during anesthesia/surgery, which may reflect brain-health vulnerability.…”

Burst Suppression During General Anesthesia and Postoperative Outcomes: Mini Review

“…Analysis of propofol-remifentanil general anesthesia maintenance in a non-cardiac surgery study found that independent factors associated with SR were advanced age, history of coronary artery disease, and male gender (Besch et al, 2011). Age-related changes in geriatric patients are associated with decreased alpha power (Kratzer et al, 2020), alpha coherence, peak frequency, and increased burst suppression occurrence (Purdon et al, 2015a). Low alpha and beta power have been linked to older age, burst suppression vulnerability, reduced brain metabolism, decreased cognition, and increased risk for postoperative complications such as POD (Plummer et al, 2019;Shao et al, 2020).…”

“…However, it is important to note that burst suppression could be overestimated due to the changes that result from aging, including low EEG voltage from cortical thinning and reduced brain volume (Purdon et al, 2015a). As geriatric patients were found to have different burst suppression patterns (Kratzer et al, 2020), provider awareness of these differences and the ability to identify these patterns are critical. Because commercial EEG algorithms do not account for age (Purdon et al, 2015a), monitoring unprocessed EEGs may better prevent adverse postoperative effects in geriatric patients.…”

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“…While most prior research on EEG as a predictor of delirium has predominantly relied on analysis of EEG data collected either intra-operatively (Kratzer et al, 2020;Sun et al, 2020) or pre-operatively (van Montfort et al, 2020), here we compared the pre-operative and intra-operative EEG signals. We observed relative changes in EEG complexity from before to during anesthesia/surgery, which may reflect brainhealth vulnerability.…”