Sevoflurane anesthesia decreases cardiac vagal activity and heart rate variability.

We evaluated cardiac vagal activity during sevoflurane anesthesia in neurosurgical patients. Heart rate variability was determined by power spectral analysis and entropy with the patient awake and during sevoflurane anesthesia. High frequency power (0.15-0.50 Hz) and heart rate entropy decreased during sevoflurane and these effects were significantly correlated (r = 0.71 +/- 0.12, P < 0.05). The results confirm that cardiac vagal activity was the primary determinant of heart rate variability, which was attenuated by sevoflurane.