Significance and characteristics of Dexmedetomidine or Propofol-induced segmental electroencephalogram power spectra

Abstract Background: Although the electroencephalogram patterns induced by dexmedetomidine and propofol are relatively similar, these drugs may have different molecular targets and involvement of distinct neural circuit dynamics in their effects. Our aim was to identify special neurophysiology signatures induced by these drugs.Methods: Forty seven patients receiving combined spinal epidural anesthesia (CSEA）were randomly divided into two groups: Dexmedetomidine group (D group, n = 24) and Propofol group (P group, n = 23). Dexmedetomidine at 1 μg/kg was administered intravenously in 10 min, then adjusted to a rate of 0.5 μg/kg/h and withheld if Ramsey sedation scale (RSS) reached 4 - 5. Propofol was given via a computer-controlled infusion to target a concentration of 0.5 μg/mL at the effect site and then to gradually increase the concentration 0.5 μg/mL every 5 min until satisfactory sedation was achieved. The vital signs, segmental Narcotrend EEG power spectra and arterial blood analysis results were recorded before sedation, and 0, 5, 10 and 15 min after drug administration ended.Results: After satisfactory sedation was achieved (RSS 4 - 5), propofol sedation was characterized with alpha wave, and dexmedetomidine sedation was characterized with theta wave.; After drug administration ended, relative power in alpha and beta waves of P group was higher than D group（P＜0.05); However, when patients were croused or patted on their shoulders, relative power in alpha, beta and theta was increased（P＜0.05) and relative power in delta wave was decreased（P＜0.05）in D group; The percentages of alpha and theta power were decreased gradually at drug withdrawal, 5min, 10min, 15min after drug administration ended; Narcotrend data have a good correlation with propofol sedation depth compared with the traditional sedation score.Conclusion: Distinct EEG patterns are induced by propofol and dexmedetomidine. Since patients sedated with dexmedetomidine may be easier to be waked up than those with propofol, this phenomenon may be associated with the lower alpha power percentage, a more easily blocked alpha wave and a higher excitability of delta wave under dexmedetomidine sedation.