Abstract
Sedation induces changes in electroencephalography (EEG) dynamics. However, the distinct EEG dynamic characteristics at comparable sedation levels have not been well studied, resulting in potential interpretation errors in EEG monitoring during sedation. We aimed to analyze the EEG dynamics of dexmedetomidine and propofol at comparable sedation levels and to explore EEG changes with increased sedation levels for each agent. We measured the Bispectral Index (BIS) and 20-channel EEG under dexmedetomidine and propofol sedation from wakefulness, moderate sedation, and deep sedation to recovery in healthy volunteers (n = 10) in a randomized, 2-day, crossover study. Observer’s Assessment of Alertness and Sedation (OAA/S) score was used to assess sedation levels. Despite similar changes in increased delta oscillations, multiple differences in the EEG spatiotemporal dynamics were observed between these two agents. During moderate sedation, both dexmedetomidine and propofol induced increased spindle power; however, dexmedetomidine decreased the global alpha/beta/gamma power, whereas propofol decreased the alpha power in the occipital area and increased the global spindle/beta/gamma power. During deep sedation, dexmedetomidine was associated with increased fronto-central spindle power and decreased global alpha/beta/gamma power, but propofol was associated with increased theta/alpha/spindle/beta power, which was maximized in the frontal area. The transition of topographic alpha/spindle/beta power distribution from moderate sedation to deep sedation completely differed between these two agents. Our study demonstrated that there was a distinct hierarchy of EEG changes with increased sedation depths by propofol and dexmedetomidine. Differences in EEG dynamics at the same sedation level might account for differences in the BIS value and reflect the different sedation mechanisms. EEG-based clinical sedation monitoring should consider the effect of drug types on EEG dynamics.
Highlights
Sedation is a state of altered consciousness induced by different kinds of anesthetics
There were no significant differences in the time from wakefulness to moderate sedation or the time from moderate sedation to deep sedation between dexmedetomidine and propofol sedation (P = 0.81 and P = 0.55, respectively); the time from deep sedation to recovery during dexmedetomidine sedation was significantly longer than that of propofol (P
2) During deep sedation, dexmedetomidine was associated with increased global theta power and fronto-central spindle power and decreased alpha/beta/gamma power across the whole cortex, but propofol was associated with increased theta/alpha/spindle/beta power, which was maximized in the frontal area
Summary
Sedation is a state of altered consciousness induced by different kinds of anesthetics. Sedation can provide a comfortable experience for the patient and a better operating condition for the clinician during unpleasant diagnostic or therapeutic procedures, and it is widely performed in operating rooms and non-operating sites[1,2,3]. Conscious sedation is a state that allows patients to tolerate unpleasant procedures when they are awake and collaborative, while deep sedation provides a condition of no response to auditory stimuli or noxious stimulation[4, 5]. More studies have focused on the transition from wakefulness to unconsciousness, and the different levels of sedation are not well characterized by EEG[6, 7]
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