Intracranial electroencephalographic changes in deep anesthesia

Area of Science:

• Neuroscience
• Anesthesiology
• Medical Devices

Background:

• Scalp electroencephalograms (EEGs) are known to show electrical silence during deep anesthesia and brain death.
• Previous studies have not reported on intracranial EEG changes specifically within the context of deep anesthesia.

Purpose of the Study:

• To report the first findings on intracranial EEG activity during deep anesthesia.
• To investigate the utility of a novel direct brain monitoring system for intracranial EEG recordings.

Main Methods:

• Development of a new direct brain monitoring system for intracranial EEGs.
• Inclusion of 13 patients with head trauma or cerebrovascular accident undergoing deep anesthesia.
• Recording intracranial EEGs and comparing them with scalp EEGs.

Main Results:

• Intracranial EEGs demonstrated distinct wave activity patterns at brain depth compared to the cortical surface.
• Scalp EEGs showed flat tracings in some cases at 2.0-2.5% isoflurane, with concurrent electrical silence in intracranial EEGs.
• Decreasing isoflurane revealed 'revival' theta waves and burst-wave activity in intracranial EEGs, indicating brain activity not visible on scalp recordings.

Conclusions:

• Intracranial EEGs reveal brain wave activity differences in the brain's depth that are undetectable by scalp EEGs.
• Intracranial EEGs can identify early indicators of brain revival following periods of near-flat tracing during deep anesthesia.