Effects of propofol on high-density EEG in disorders of consciousness: An exploratory study of patient-specific neurophysiological modulation

INTRODUCTION: This exploratory study examined the lingering effects of a short propofol sedation using high-density electroencephalography (hd-EEG) in brain-injured patients in disorders of consciousness (DoC). Since the sedative zolpidem can induce paradoxical arousal in 5-10% of this population, we hypothesized that propofol, sharing the GABA-A receptor agonist structure, might produce similar effects after the sedation period. METHODOLOGY: Nineteen non-sedated patients following severe brain injury (47.2 ± 19.1 years; 12 females) were included, encompassing diverse etiologies (traumatic, ischemic-hypoxic, hemorrhagic, stroke), diagnoses (3 coma, 14 unresponsive wakefulness syndrome [UWS], 2 minimally conscious state [MCS]), and recovery stages. Hd-EEG was recorded before and after sedation to assess spectral (relative power, spectral ratios, ABCD classification) and connectivity (weighted phase lag index, graph theoretical properties) features. Marker changes were classified as 'positive' or 'negative' based on prior associations with higher levels of consciousness in sleep, anesthesia, and DoC studies. RESULTS: Most patients exhibited significant changes in spectral and connectivity markers; however, the direction of change varied across markers within individuals, suggesting that no individual marker suffices to capture the brain's response. Distinct effect profiles emerged. Marker values did not correlate with time since injury, time since sedation cessation, sedation duration, age, or Coma Recovery Scale-Revised (CRS-R) score. CONCLUSION: Although several factors limit interpretation (heterogeneity of our patient population, phase post-injury, sedation duration), this proof-of-concept work allows exploration of propofol's effects across diverse brain injury profiles. Interestingly, propofol appears to have patient-specific electrophysiological effects and enhances spectral and functional dynamics in select DoC patients. Further work is needed to identify characteristics shared by patients who exhibit seemingly positive responses.