Nonlinear changes in brain dynamics during emergence from sevoflurane anesthesia: preliminary exploration using new software
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Published on: January 13, 2018
Peter T Walling1, Kenneth N Hicks
1Department of Anesthesia and Pain Management, University of Texas Southwestern Medical Center, Dallas, Texas, USA. quailrf@airmail.net
Background:
New software was used during a pilot study of nonlinear changes in the electroencephalogram during emergence from sevoflurane anesthesia.
Methods:
Digitized electroencephalographic signals were recorded from bipolar forehead electrodes between 1.2 and 40 k s/sec. Trajectories derived from underlying attractors were displayed continuously, and attractor dimensions were estimated. Observations are reported from 13 patients emerging from sevoflurane anesthesia.
Results:
Qualitative observations and quantitative analysis of the data demonstrated four dynamical stages during emergence from deep anesthesia to consciousness.
Conclusions:
The dynamical stages of emergence from sevoflurane anesthesia into consciousness demonstrate a classic route toward chaos, but the presence of chaos in the conscious state remains unproven. These stages are apparent both pictorially and analytically. Pre-emergent attractor patterns are usually distinctive; their real-time display could be a useful adjunct to depth of anesthesia monitors because they may provide warning of an imminent return to consciousness.
