LAUSR

Purpose The effects of remimazolam on autonomic nervous activity have not been elucidated. We investigated the differential effects of remimazolam and propofol on autonomic nervous activity during anesthesia induction. Methods Thirty patients were randomly divided into a remimazolam group or a propofol group for anesthesia induction. Hemodynamics and indices of heart rate variability were recorded before and after anesthesia. Low frequency power (LF; 0.04–0.15 Hz, ms 2 ) and high frequency power (HF; 0.15–0.4 Hz, ms 2 ) were calculated from power spectral density of heart rate variability. LF reflects both sympathetic and parasympathetic activities and HF reflects parasympathetic activity. To investigate the balance between sympathetic and parasympathetic activities, the normalized unit (%) of LF (LF nu) and that of HF (HF nu) were calculated. Changes in LF nu (ΔLF nu) before and after anesthesia (ΔLF nu = LF nu at awake—LF nu after anesthesia) were compared between the groups. Results Remimazolam and propofol decreased blood pressure and power spectral density of heart rate variability. Remimazolam did not change LF nu and HF nu, while propofol increased LF nu and decreased HF nu ( P  = 0.020). ΔLF nu in the remimazolam group (1.4 ± 23.6%) were less than that in the propofol group (19.3 ± 22.4%, P  = 0.0415). Conclusion Remimazolam and propofol decreased autonomic nervous activity during anesthesia induction. Remimazolam preserved the balance of sympathetic and parasympathetic activities, while propofol modulated it to sympathetic dominance.