Authors: Obert DP et al.
Anesthesia & Analgesia. 142(1):32–40, January 2026.
Summary
This study evaluated whether commonly used processed EEG indices can distinguish between specific electroencephalographic emergence trajectories that have previously been associated with postoperative neurocognitive disorders (PNDs). Earlier work identified three distinct emergence patterns: a favorable reference trajectory characterized by gradual progression from delta-dominant slow-wave anesthesia through spindle-dominant slow-wave activity and non–slow-wave activity before awakening; an abrupt trajectory transitioning directly from delta-dominant slow-wave anesthesia to wake; and a high trajectory in which patients emerge from non–slow-wave anesthesia directly to wake. The latter two trajectories are associated with markedly increased odds of developing PND.
Using EEG recordings from 59 patients, the authors replayed emergence EEG data into four neuromonitoring devices using an EEG player: state entropy (SE), bispectral index (BIS), quantium consciousness index (qCON), and Patient State Index (PSI). Index behavior was then compared across the three emergence trajectories. SE and PSI best differentiated the favorable reference trajectory from the abrupt trajectory across much of emergence. Patients following the reference trajectory showed a smooth, near-linear increase in index values, whereas abrupt trajectories demonstrated persistently low index values followed by a rapid rise near awakening. In contrast, qCON, PSI, and BIS were more effective at distinguishing the reference trajectory from the high trajectory early in emergence, reflecting the fact that patients in the high trajectory began emergence in non–slow-wave anesthesia with already elevated index values.
The findings show that processed EEG indices do reflect underlying spectral EEG changes during emergence, but their ability to distinguish clinically relevant emergence trajectories varies by device. No single index reliably differentiates all trajectories, emphasizing the importance of understanding how individual monitors process EEG signals when interpreting emergence patterns.
What You Should Know
Distinct EEG emergence trajectories linked to postoperative neurocognitive disorders produce different patterns on processed EEG monitors.
Depth-of-anesthesia indices are trajectory- and device-specific; absolute values are less informative than trends over time.
SE and PSI are more sensitive to distinguishing gradual versus abrupt emergence, while BIS, qCON, and PSI better identify high-index emergence patterns early.
Monitoring index trajectories during emergence may help anesthesiologists recognize patients at elevated risk for PND before PACU arrival.
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