# Characterizing Canine Frontal Electroencephalographic Patterns and Cardiovascular Correlates at Different Anesthetic Levels of Sevoflurane

## TL;DR

This study shows how sevoflurane anesthesia affects brain activity and blood pressure in dogs, suggesting blood pressure could help monitor anesthetic levels.

## Contribution

The study identifies distinct EEG patterns and their correlation with blood pressure during sevoflurane anesthesia in dogs.

## Key findings

- EEG patterns changed predictably with increasing sevoflurane levels, from awake to burst suppression and electrical silence.
- Blood pressure correlated with EEG changes, but heart rate did not, indicating blood pressure is a better anesthetic indicator.
- Processed EEG indices and MBP suggest sevoflurane disrupts cortical communication to induce anesthesia and antinociception.

## Abstract

This study investigated brain activity (using frontal electroencephalogram [EEG]) and cardiovascular responses in dogs anesthetized with different concentrations of sevoflurane. We found that EEG patterns changed predictably with increasing anesthetic levels, progressing from awake patterns to burst suppression and electrical silence. These EEG changes correlated with blood pressure but not heart rate, suggesting blood pressure may be a better indicator of anesthetic level in dogs. Our findings also reveal distinct brainwave features associated with sevoflurane anesthesia, suggesting this drug disrupts cortical communication to induce anesthesia and antinociception. This highlights the potential of real-time EEG monitoring with blood pressure to individualize anesthesia and improve procedural outcomes in dogs.

This study evaluated electroencephalogram [EEG] and cardiovascular correlation of sevoflurane anesthesia in healthy beagle dogs at varying minimum alveolar concentration (MAC) multiples. Processed EEG indices (Patient State Index [PSI], burst suppression ratio [SR], and Spectral Edge Frequency [SEF95], cardiovascular parameters (mean blood pressure [MBP], heart rate [HR]), and responses to noxious (electrical) stimuli were recorded. Deep anesthesia (2.5x MAC) resulted in the lowest PSI and MBP values (13.5 ± 9.9, 42.2 ± 7.4 mmHg, respectively), the highest SR (52.7 ± 35.4%), and dominant burst suppression. Surgical anesthesia (1.5x MAC) was characterized by alpha/low beta waves and the absence of response to noxious stimuli. At 1x MAC (2.1%), PSI and MBP increased (41.9 ± 12.6, 119.9 ± 17.7, respectively) while SR decreased (7.1 ± 13%). A moderate PSI-MBP correlation (ρ = 0.48, p = 0.002) was observed. Recovery was acceptable or smooth in most dogs. These findings suggest that sevoflurane disrupts cortical communication, inducing anesthesia and antinociception and that real-time EEG monitoring may aid in titrating sevoflurane delivery in conjunction with MBP.