Electroencephalogram Burst-suppression during Cardiopulmonary Bypass in Elderly Patients Mediates Postoperative Delirium

Abstract

Background Intraoperative burst-suppression is associated with postoperative delirium. Whether this association is causal remains unclear. Therefore, the authors investigated whether burst-suppression during cardiopulmonary bypass (CPB) mediates the effects of known delirium risk factors on postoperative delirium. Methods This was a retrospective cohort observational substudy of the Minimizing ICU [intensive care unit] Neurological Dysfunction with Dexmedetomidine-induced Sleep (MINDDS) trial. The authors analyzed data from patients more than 60 yr old undergoing cardiac surgery (n = 159). Univariate and multivariable regression analyses were performed to assess for associations and enable causal inference. Delirium risk factors were evaluated using the abbreviated Montreal Cognitive Assessment and Patient-Reported Outcomes Measurement Information System questionnaires for applied cognition, physical function, global health, sleep, and pain. The authors also analyzed electroencephalogram data (n = 141). Results The incidence of delirium in patients with CPB burst-suppression was 25% (15 of 60) compared with 6% (5 of 81) in patients without CPB burst-suppression. In univariate analyses, age (odds ratio, 1.08 [95% CI, 1.03 to 1.14]; P = 0.002), lowest CPB temperature (odds ratio, 0.79 [0.66 to 0.94]; P = 0.010), alpha power (odds ratio, 0.65 [0.54 to 0.80]; P < 0.001), and physical function (odds ratio, 0.95 [0.91 to 0.98]; P = 0.007) were associated with CPB burst-suppression. In separate univariate analyses, age (odds ratio, 1.09 [1.02 to 1.16]; P = 0.009), abbreviated Montreal Cognitive Assessment (odds ratio, 0.80 [0.66 to 0.97]; P = 0.024), alpha power (odds ratio, 0.75 [0.59 to 0.96]; P = 0.025), and CPB burst-suppression (odds ratio, 3.79 [1.5 to 9.6]; P = 0.005) were associated with delirium. However, only physical function (odds ratio, 0.96 [0.91 to 0.99]; P = 0.044), lowest CPB temperature (odds ratio, 0.73 [0.58 to 0.88]; P = 0.003), and electroencephalogram alpha power (odds ratio, 0.61 [0.47 to 0.76]; P < 0.001) were retained as predictors in the burst-suppression multivariable model. Burst-suppression (odds ratio, 4.1 [1.5 to 13.7]; P = 0.012) and age (odds ratio, 1.07 [0.99 to 1.15]; P = 0.090) were retained as predictors in the delirium multivariable model. Delirium was associated with decreased electroencephalogram power from 6.8 to 24.4 Hertz. Conclusions The inference from the present study is that CPB burst-suppression mediates the effects of physical function, lowest CPB temperature, and electroencephalogram alpha power on delirium. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New

Postoperative Delirium

“…Therefore, it is a seductive idea that the appearance of this pattern is an indicator of brain pathology and that elderly patients showing intraoperative burst suppression may then go on to develop disrupted cognitive function postoperatively. In this issue of the journal, a study by Pedemonte et al 1 replicates the results from a number of previous observational studies, showing that intraoperative burst suppression was associated with a marked increase (from 6 to 25%) in postoperative delirium after cardiac surgery. From table 1 of their article, 15 of the 20 patients who had postoperative delirium had displayed a burst suppression EEG pattern during their surgery.…”

A Processed EEG based Brain Anesthetic Resistance Index Predicts Postoperative Delirium in Older Adults: A Dual Center Study

“…40 For example, anesthetic-induced frontal alpha power decreases with age, 37 yet there is still substantial variance in alpha power among older adults. 8 In fact, Hesse and colleagues found that markers of “brain age” can predict postoperative delirium better than chronological age, perhaps due to age-dependent biological changes that occur within the brain. 7 Interestingly, chronological age was not a significant predictor of delirium in this study, which likely reflects the relative narrow age distribution of the cohorts studied here (i.e.…”

Neuromonitoring and Neurocognitive Outcomes in Cardiac Surgery: A Narrative Review

“…[134][135][136][137][138] Known POD risk factors, including limited physical function, lowest body temperature on CPB, and EEG alpha power, may increase the risk of delirium by means of their impact on burst suppression during CPB. 139 Given the relationship between hypotension and neurologic insult during cardiac surgery, some have advocated the use of EEG for monitoring of burst suppression, particularly given the increased postoperative mortality associated with concurrent hypotension and waveform suppression in a recent large RCT (ENGAGES trial), although no difference in POD incidence was noted. [140][141][142] EEG use for neuromonitoring is limited by the cumbersome application of the electrodes, requiring skill to interpret, and its primary function as a monitor of the superficial layers of the cerebral cortex.…”