Regular Article
Invariant Reversible QEEG Effects of Anesthetics

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Abstract

Continuous recordings of brain electrical activity were obtained from a group of 176 patients throughout surgical procedures using general anesthesia. Artifact-free data from the 19 electrodes of the International 10/20 System were subjected to quantitative analysis of the electroencephalogram (QEEG). Induction was variously accomplished with etomidate, propofol or thiopental. Anesthesia was maintained throughout the procedures by isoflurane, desflurane or sevoflurane (N = 68), total intravenous anesthesia using propofol (N = 49), or nitrous oxide plus narcotics (N = 59). A set of QEEG measures were found which reversibly displayed high heterogeneity of variance between four states as follows: (1) during induction; (2) just after loss of consciousness (LOC); (3) just before return of consciousness (ROC); (4) just after ROC. Homogeneity of variance across all agents within states was found. Topographic statistical probability images were compared between states. At LOC, power increased in all frequency bands in the power spectrum with the exception of a decrease in gamma activity, and there was a marked anteriorization of power. Additionally, a significant change occurred in hemispheric relationships, with prefrontal and frontal regions of each hemisphere becoming more closely coupled, and anterior and posterior regions on each hemisphere, as well as homologous regions between the two hemispheres, uncoupling. All of these changes reversed upon ROC. Variable resolution electromagnetic tomography (VARETA) was performed to localize salient features of power anteriorization in three dimensions. A common set of neuroanatomical regions appeared to be the locus of the most probable generators of the observed EEG changes.

References (38)

  • A. Fernandez-Bouzas et al.

    EEG Frequency Domain distributed inverse solutions in lesions

    EEG Clinical Neurophysiology

    (1997)
  • A. Fernandez-Bouzas et al.

    Sources of abnormal EEG activity in the presence of brain lesions

    Clinical EEG

    (1999)
  • P.T. Fiset et al.

    Brain mechanisms of propofol-induced loss of consciousness in humans: A positron emission tomographic study

    Journal of Neuroscience

    (1999)
  • P.S. Glass et al.

    Bispectral analysis measures sedation and memory effects propofol, midazolam, isoflurane, and alfentanil in healthy volunteers

    Anesthesiology

    (1997)
  • T. Harmony et al.

    Frequency source analysis in patients with brain lesions

    Brain Topography

    (1995)
  • N. Hofle et al.

    Regional Cerebral Blood Flow changes as a function of delta and spindle activity during slow wave sleep in humans

    Journal of Neuroscience

    (1997)
  • J.R. Hughes et al.

    Conventional and quantitative electroencephalography in Psychiatry

    Journal of Neuropsychiatry Clinical Neuroscience

    (1999)
  • E.R. John et al.

    Principles of neurometrics and neurometric analysis of EEG and evoked potentials

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    This article is part of a special issue of this journal on A Consciousness Monitor.

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    To whom correspondence and reprint requests should be addressed. E-mail: johnr01@popmail. med.nyu.edu.

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