BACKGROUND: General anesthesia alters autonomic nervous system activity. Evaluation of the autonomic nervous system activity using heart rate variability and so, evaluating the anesthetic depth was tried.

METHODS: In thirty patients undergoing gynecological surgery under general inhalational anesthesia with enflurane, a 10-minute EKG was perioperatively acquired during main incidents. The heart rate variability was analyzed and expressed as 5-minute signals.

RESULTS: In an analysis of the frequency area adopting the heart rate variability, both low and high frequencies represented the effects of the autonomic nervous system, but the low and high frequencies, their ratio and 1/f noise were not valuable in estimating the depth of anesthesia before, during and after the operation. The detrended fluctuation analysis also proved unsuitable for the estimation of the anesthetic depth during an operation.

CONCLUSIONS: The signal using heart rate variability reflects the parameter of the autonomic nervous system during operations.