Authors: Dragovic S Z et al.
Source: Anesthesia & Analgesia. February 2026. Volume 142(2):249–260. DOI: 10.1213/ANE.0000000000007530
Summary:
Processed EEG indices are widely used to guide anesthetic depth, yet most clinical paradigms implicitly assume that equivalent index values reflect comparable brain states across different anesthetic agents. In this retrospective study, Dragovic and colleagues challenge that assumption by demonstrating systematic EEG spectral differences between propofol and volatile anesthetics, even when anesthetic depth is clinically matched.
The authors analyzed steady-state frontal EEG recordings from 108 patients undergoing general anesthesia with either propofol or fluranes (sevoflurane or desflurane). Conventional spectral measures were compared with two newer analytic approaches—fitting oscillations and one-over-f, and variational mode decomposition—at clinically guided hypnotic and analgesic levels. Analyses were further stratified by spectral edge frequency (SEF) ranges to assess whether differences persisted across commonly targeted EEG bandwidths.
While sevoflurane and desflurane showed similar EEG patterns, propofol anesthesia consistently demonstrated higher dominant frequencies and lower aperiodic exponents than fluranes across both novel analytic methods. Variational mode decomposition identified approximately a 1.5 Hz higher central frequency under propofol compared to fluranes, with strong discrimination between groups. Fitting oscillations and one-over-f yielded even larger frequency differences and also revealed reduced spectral exponents under propofol, suggesting fundamental distinctions in cortical dynamics rather than measurement artifact. These differences persisted across both lower and higher SEF ranges, underscoring that agent-specific EEG signatures remain even when conventional parameters imply comparable anesthetic depth.
The findings highlight an important limitation of current one-size-fits-all EEG indices and suggest that anesthetic-specific brain states may be obscured when disparate agents are titrated to identical processed EEG targets. By leveraging newer analytical methods, the study offers a path toward more physiologically meaningful, agent-specific neurophysiologic monitoring.
What You Should Know:
• Equivalent processed EEG values do not necessarily represent equivalent brain states across anesthetic agents.
• Propofol and fluranes produce distinct EEG spectral signatures even at comparable clinical depths of anesthesia.
• Novel analytic approaches uncover differences that conventional spectral metrics may miss.
• Agent-specific EEG indices may improve accuracy and safety in anesthetic depth monitoring.
Key Points:
• Propofol is associated with higher dominant EEG frequencies than volatile anesthetics.
• Differences are consistently detected using variational mode decomposition and fitting oscillations & one-over-f.
• Traditional EEG assumptions may introduce bias when comparing anesthetic agents.
• These methods support future development of anesthetic-specific EEG monitoring tools.
Thank you to Anesthesia & Analgesia for publishing this methodologically innovative study that challenges long-standing assumptions in anesthetic EEG monitoring and advances the field toward more precise, agent-aware neurophysiologic assessment.