Article (Scientific journals)
The spectral exponent of the resting EEG indexes the presence of consciousness during unresponsiveness induced by propofol, xenon, and ketamine
Colombo, M. A.; Napolitani, Martino; Boly, Mélanie et al.
2019In NeuroImage, 189, p. 631-644
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Keywords :
Anesthesia; Consciousness; E/I; EEG; NCC; Article; Ramsay Sedation Scale
Abstract :
[en] Despite the absence of responsiveness during anesthesia, conscious experience may persist. However, reliable, easily acquirable and interpretable neurophysiological markers of the presence of consciousness in unresponsive states are still missing. A promising marker is based on the decay-rate of the power spectral density (PSD) of the resting EEG. We acquired resting electroencephalogram (EEG) in three groups of healthy participants (n = 5 each), before and during anesthesia induced by either xenon, propofol or ketamine. Dosage of each anesthetic agent was tailored to yield unresponsiveness (Ramsay score = 6). Delayed subjective reports assessed whether conscious experience was present (‘Conscious report’) or absent/inaccessible to recall (‘No Report’). We estimated the decay of the PSD of the resting EEG—after removing oscillatory peaks—via the spectral exponent β, for a broad band (1–40 Hz) and narrower sub-bands (1–20 Hz, 20–40 Hz). Within-subject anesthetic changes in β were assessed. Furthermore, based on β, ‘Conscious report’ states were discriminated against ‘no report’ states. Finally, we evaluated the correlation of the resting spectral exponent with a recently proposed index of consciousness, the Perturbational Complexity Index (PCI), derived from a previous TMS-EEG study. The spectral exponent of the resting EEG discriminated states in which consciousness was present (wakefulness, ketamine) from states where consciousness was reduced or abolished (xenon, propofol). Loss of consciousness substantially decreased the (negative) broad-band spectral exponent in each subject undergoing xenon or propofol anesthesia—indexing an overall steeper PSD decay. Conversely, ketamine displayed an overall PSD decay similar to that of wakefulness—consistent with the preservation of consciousness—yet it showed a flattening of the decay in the high-frequencies (20–40 Hz)—consistent with its specific mechanism of action. The spectral exponent was highly correlated to PCI, corroborating its interpretation as a marker of the presence of consciousness. A steeper PSD of the resting EEG reliably indexed unconsciousness in anesthesia, beyond sheer unresponsiveness. © 2019 The Authors
Disciplines :
Neurology
Author, co-author :
Colombo, M. A.;  Neurosurgical Intensive Care, ASST Grande Ospedale Metropolitano Niguarda, Milan, 20162, Italy
Napolitani, Martino;  Dipartimento di Scienze Biomediche e Cliniche “L. Sacco”, Università Degli Studi di Milano, Milan, 20157, Italy, Department of Health Science, School of Medicine and Surgery, University of Milan-Bicocca, Monza, Italy
Boly, Mélanie;  Department of Neurology and Department of Psychiatry, University of Wisconsin, Madison, United States
Gosseries, Olivia  ;  Université de Liège - ULiège > Consciousness-Coma Science Group
Casarotto, Silvia;  Dipartimento di Scienze Biomediche e Cliniche “L. Sacco”, Università Degli Studi di Milano, Milan, 20157, Italy
Rosanova, Mario;  Dipartimento di Scienze Biomediche e Cliniche “L. Sacco”, Università Degli Studi di Milano, Milan, 20157, Italy, Fondazione Europea per La Ricerca Biomedica, Milan, Italy
Brichant, Jean-François ;  Université de Liège - ULiège > Département des sciences cliniques > Anesthésie et réanimation
Boveroux, Philippe ;  Université de Liège - ULiège > Faculté des sciences sociales > Economie politique et économie de la santé
Rex, S.;  Department of Anaesthesiology and Department of Cardiovascular Sciences, University Hospitals of the KU Leuven, KU Leuven, Leuven, 3000, Belgium
Laureys, Steven  ;  Université de Liège - ULiège > Consciousness-Coma Science Group
Massimini, Marcello;  Dipartimento di Scienze Biomediche e Cliniche “L. Sacco”, Università Degli Studi di Milano, Milan, 20157, Italy, Istituto Di Ricovero e Cura a Carattere Scientifico, Fondazione Don Carlo Gnocchi, Milan, 20148, Italy
Chieregato, A.;  Neurosurgical Intensive Care, ASST Grande Ospedale Metropolitano Niguarda, Milan, 20162, Italy
Sarasso, Simone;  Dipartimento di Scienze Biomediche e Cliniche “L. Sacco”, Università Degli Studi di Milano, Milan, 20157, Italy
More authors (3 more) Less
Language :
English
Title :
The spectral exponent of the resting EEG indexes the presence of consciousness during unresponsiveness induced by propofol, xenon, and ketamine
Publication date :
2019
Journal title :
NeuroImage
ISSN :
1053-8119
eISSN :
1095-9572
Publisher :
Academic Press Inc.
Volume :
189
Pages :
631-644
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 17 January 2020

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