The relationship of heart rate between natural sleep and dexmedetomidine sedation.

Background: Sedation by dexmedetomidine is similar to natural sleep and often causes bradycardia. We attempted to determine the relationship of heart rate changes between natural sleep and dexmedetomidine sedation.

Methods: The present study included 30 who were scheduled to undergo elective surgery under spinal anesthesia. To assess heart rate (HR) and sedation, pulse oximeter and bispectral index (BIS) monitor were attached to the patient in the ward and the operating room. After measuring the HR and BIS before sleep, the BIS decreased to less than 70 and the HR and BIS were measured at 5 min intervals. HR and BIS were measured before spinal anesthesia, and HR and BIS were measured at 5 min interval after dexmedetomidine injection.

Results: At natural sleep, heart rate changes ranged from 2 to 19 beats/min (13.4 ± 4.4 beats/min), while in dexmedetomidine sedation from 9 to 40 beats/min (25.4 ± 8.5 beats/min). Decrease in heart rate was significantly correlated between natural sleep and dexmedetomidine sedation (R2=0.41, P < 0.001). The lowest heart rate was 59 beats/min at 66 minutes in natural sleep and 55 beats/min at 13 min in dexmedetomidine sedation. There was a difference in the time of the lowest heart rate (P < 0.001) but there was no difference in the rate (P = 0.09).

Conclusions: There was a correlation between the change in heart rate during natural sleep and dexmedetomidine sedation. The bradycardia that occurs when using dexmedetomidine may be one of the normal changes, and this may be observed rather than corrected.