Work

EEG signatures at ascending vs descending propofol vs sevoflurane concentrations analyzed with BIS and a State-Chart Score

Year: 2026

Type: preprint

Abstract: Background Depth of anesthesia is routinely monitored using electroencephalo-graphic (EEG) indices such as the Bispectral Index (BIS), which reduce cortical activity to a single numerical real-time series. However, these scalar descriptors fail to capture inter-individual variability, drug-specific EEG signatures, and transitions between brain states. Methods We analyzed transient EEG patterns during general anesthesia induced by propofol and sevoflurane in 89 patients. Iso-electric suppressions (IES), α -suppressions, and spectral power in the α and δ bands were quantified across controlled concentration plateaus. We compared conventional BIS monitoring with a novel State-Chart representation mapping EEG activity into discrete depth states. Results Increasing hypnotic concentration produced a consistent shift from α -dominant to δ -dominant activity and a reduction in maximal α frequency. IES occurred predominantly at high propofol concentrations and remained infrequent under sevoflurane. Compared with BIS, the State-Chart showed a marked reduction in temporal variability (0.5 ± 0.6 vs 4.0 ± 2.9; p < 10 −90 ). Importantly, our State-Chart separates stable from transition regimes and discriminates identical concentration levels. Statistics computed over prior dosing (ascending vs descending), reveals refined clustering not captured by BIS. Conclusions Anesthesia depth drugs concentrations vs EEG effects is more accurately described by structured EEG state transitions than by a single numerical index. The State-Chart provides a stable, physiologically interpretable representation of brain activity and reveals transition states preceding deep cortical suppression, supporting individualized and predictive monitoring of anesthesia.

Source: medRxiv

DOI: 10.64898/2026.10.03.26364648