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Early Quantitative Gamma-Band EEG Marker is Associated with Outcomes After Cardiac Arrest and Targeted Temperature
Ruoxian Deng1, Matthew A Koenig, Leanne Moon Young
1Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
Background:
Brain recovery after cardiac arrest (CA) is sensitive to temperature. Yet the effect of temperature management on different EEG frequency bands has not been elucidated. A novel quantitative EEG algorithm, sub-band information quantity (SIQ), was applied to evaluate EEG recovery and outcomes after CA.
Methods:
Twenty-four Wistar rats undergoing 7-min CA were randomly assigned to immediate hypothermia (32-34 °C), normothermia (36.5-37.5 °C), or hyperthermia (38.5-39.5 °C) (n = 8). EEG was recorded continuously for the first 8 h and then for serial 30-min epochs daily. The neurologic deficit score (NDS) at 72-h was the primary functional outcome. Another four rats without brain injury were added as a control.
Results:
Better recovery of gamma-band SIQ was found in the hypothermia group (0.60 ± 0.03) compared with the normothermia group (0.40 ± 0.03) (p < 0.01) and in the normothermia group compared with the hyperthermia group (0.34 ± 0.03) (p < 0.05). The NDS was also improved in the lower temperature groups: hypothermia [median (25th, 75th), 74 (61, 74)] versus normothermia [49 (47, 61)] versus hyperthermia [43 (0, 50)] (p < 0.01). Throughout the 72-h experiment, the gamma-band SIQ showed the strongest correlation at every time point (ranging 0.520-0.788 from 30-min to 72-h post-resuscitation, all p < 0.05) whereas the delta-band SIQ had poor correlation with the 72-h NDS. No significant difference of sub-band EEG was found with temperature manipulation alone.
Conclusions:
Recovery of gamma-band SIQ-qEEG was strongly associated with functional outcomes after CA. Induced hypothermia was associated with faster recovery of gamma-band SIQ and improved functional outcomes. Targeted temperature management primarily affected gamma frequency oscillations but not delta rhythm.
