Duration of EEG suppression does not predict recovery time or degree of cognitive impairment after general anaesthesia in human volunteers

Abstract

Background: Burst suppression occurs in the EEG during coma and under general anaesthesia. It has been assumed that burst suppression represents a deeper state of anaesthesia from which it is more difficult to recover. This has not been directly demonstrated, however. Here, we test this hypothesis directly by assessing relationships between EEG suppression in human volunteers and recovery of consciousness. Methods: We recorded the EEG of 27 healthy humans (nine women/18 men) anaesthetised with isoflurane 1.3 minimum alveolar concentration (MAC) for 3 h. Periods of EEG suppression and non-suppression were separated using principal component analysis of the spectrogram. After emergence, participants completed the digit symbol substitution test and the psychomotor vigilance test. Results: Volunteers demonstrated marked variability in multiple features of the suppressed EEG. In order to test the hypothesis that, for an individual subject, inclusion of features of suppression would improve accuracy of a model built to predict time of emergence, two types of models were constructed: one with a suppression-related feature included and one without. Contrary to our hypothesis, Akaike information criterion demonstrated that the addition of a suppression-related feature did not improve the ability of the model to predict time to emergence. Furthermore, the amounts of EEG suppression and decrements in cognitive task performance relative to pre-anaesthesia baseline were not significantly correlated. Conclusions: These findings suggest that, in contrast to current assumptions, EEG suppression in and of itself is not an important determinant of recovery time or the degree of cognitive impairment upon emergence from anaesthesia in healthy adults.

Recovery of Consciousness and Cognition after General Anesthesia in Humans

“…Anesthetized subjects continued to inhale 1.3 age-adjusted MAC isoflurane anesthesia for three hours. Burst suppression, a sign of deep anesthesia, was found to be associated with this concentration of isoflurane in this cohort (Hemmings et al, 2019;Shortal et al, 2019). Blood pressure was targeted to remain within 20% of baseline pre-induction values using a phenylephrine infusion or intermittent boluses of ephedrine, as necessary.…”

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

“…Other studies could not show this relationship (Shortal et al, 2019;Wildes et al, 2019). In particular, the study by Shortal et al shows that young volunteers may not be affected by BSUPP (Shortal et al, 2019). But these studies use different tools and criteria to identify burst suppression.…”

“…Several studies highlighted a possible association between this intraoperative EEG pattern and delirium in the postoperative care unit (Hesse et al, 2019) or postoperative delirium (Soehle et al, 2015;Fritz et al, 2016). Other studies could not show this relationship (Shortal et al, 2019;Wildes et al, 2019). In particular, the study by Shortal et al shows that young volunteers may not be affected by BSUPP (Shortal et al, 2019).…”

Protocol for the Prognosticating Delirium Recovery Outcomes Using Wakefulness and Sleep Electroencephalography (P-DROWS-E) study: a prospective observational study of delirium in elderly cardiac surgical patients

“…Secondary analytical models will include relevant medications and comorbidities such as obstructive sleep apnea and depression as well as years of education. Additional covariates to account for intraoperative anaesthetic exposure will use intraoperative measures of SWA, sleep spindle density and burst suppression [171][172][173] derived from intraoperative EEG device recordings. As we expect that only 25% of our patients may develop postoperative delirium, we will consider zero-inflated models.…”