Monitoring Anesthetic Brain States - Electroencephalogram-Based Indices of Level of Consciousness
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Electroencephalogram-Based Indices of Level of Consciousness
It is recognized that the EEG changes systematically in relation to the dose of anesthetic drug administered. As a consequence, the unprocessed EEG and various forms of processed EEG have been used to track the level of consciousness of patients receiving general anesthesia and sedation.
- Basic Biophysics of EEG
- The EEG detects postsynaptic potentials in the cerebral cortex. As neurons synapse in a region of the cortex, they produce macroscopic extracellular currents that can be detected as potential differences by surface electrodes. The cortex is tied to subcortical structures like the thalamus.
- Therefore with the EEG, inferences can be made about both cortical and subcortical dynamics.
- The EEG signals are comprised of oscillations or waves with a variety of frequencies.