Heart rate variability during abdominal surgical manipulation under general and epidural anesthesia.

Anesthesiologists occasionally encounter bradycardia during abdominal surgery and recognize the phenomenon as a vagal reflex. The presence of bradycardia implies efferent vagal dominance in the autonomic nervous system during this vagal reflex. In this study, we investigated the effect of abdominal surgical manipulation on autonomic nervous activity, using heart rate variability analysis. Abdominal surgical manipulation decreased the heart rate and enhanced not only the high-frequency power (0.15-0.4 Hz) but also the low-frequency power (0.04-0.15 Hz) calculated from the power spectral density of heart rate variability. Our results suggest that both vagal tone and sympathetic tone could be activated during the vagal reflex caused by abdominal surgical manipulation.