Assessing nitrous oxide effect using electroencephalographically-based depth of anesthesia measures cortical state...

Area of Science:

• Anesthesiology
• Neuroscience
• Biomedical Engineering

Background:

• Current electroencephalography (EEG) depth of anesthesia monitors struggle with n-methyl-D-aspartate (NMDA) receptor antagonist anesthetics like ketamine and nitrous oxide (N2O).
• Reliable monitoring is crucial for patient safety during anesthesia, especially with agents that affect brain activity differently.

Purpose of the Study:

• To explore the efficacy of a novel algorithm using autoregressive-moving-average (ARMA) modeling for monitoring anesthesia depth during N2O administration.
• To evaluate new metrics, Composite Cortical State (CCS) and Composite Cortical State distance (CCSd), derived from Cortical State (CS) and Cortical Input (CI), for tracking N2O levels and patient responsiveness.

Main Methods:

• Retrospective application of an ARMA-based algorithm to EEG data from healthy individuals exposed to varying concentrations of N2O (20%, 40%, 60%).
• Analysis of Cortical State (CS), Cortical Input (CI), Composite Cortical State (CCS), and Composite Cortical State distance (CCSd) in relation to N2O concentration and responsiveness.

Main Results:

• Significant reductions in responsiveness were observed at 50-60% N2O peak gas levels.
• CS and CCS increased by 39% and 42% respectively, while CCSd decreased by 398% at higher N2O concentrations.
• Cortical Input (CI) changes were inconclusive, requiring further investigation with larger sample sizes or higher concentrations.

Conclusions:

• The novel CS, CCS, and particularly CCSd measures derived from frontal EEG show potential for differentiating N2O concentrations and responsiveness levels.
• These metrics offer an advantage over existing methods for monitoring NMDA receptor antagonist-based anesthesia.
• Further research is needed to validate CI and assess the sensitivity of CS-based measures to other anesthetics in clinical settings.