Effects of sugammadex on heart rate variability in anesthetized male rats

The administration of sugammadex has been associated with bradycardia and rarely asystole; however, the underlying mechanisms remain unclear. We examined heart rate variability (HRV) as an index of autonomic nervous system activity and investigated the effects of sugammadex on HRV in α-chloralose and urethane anesthetized male rats. In protocol 1, we examined the effect of intravenous administration of sugammadex (10 mg/kg) alone. In protocol 2, sugammadex was administered 3 min after the administration of rocuronium bromide. In protocol 3, the effect of sugammadex was assessed after vagotomy. Sugammadex significantly prolonged the mean R-R interval and increased time domain HRV indices, total power, high-frequency power, and low-frequency power. Rocuronium prior to sugammadex did not affect sugammadex-induced percent changes in HRV indices. Prior vagotomy abolished the effects of sugammadex on HRV. These results suggest that sugammadex prolonged the mean R-R interval and augmented HRV indices via vagal activation.