Investigation of the Effects of Continuous Low-Dose Epidural Analgesia on the Autonomic Nervous System Using Hilbert Huang Transform

Wei-Ren Chuang,Li-Kuei Chen,Yin-Yi Han,Jia-Rong Yeh,Jiann-Shing Shieh

doi:10.1260/2040-2295.1.1.13

Wei-Ren Chuang, Li-Kuei Chen + Show 3 more

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https://doi.org/10.1260/2040-2295.1.1.13

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Abstract

Effects of continuous low-dose epidural bupivacaine (0.05-0.1%) infusion on the Doppler velocimetry for labor analgesia have been well documented. The aim of this study was to monitor the activity of the autonomic nervous system (ANS) for women in labor based on Hilbert Huang transform (HHT), which performs signal processing for nonlinear systems, such as human cardiac systems. Thirteen pregnant women were included in the experimental group for labor analgesia. They received continuous epidural bupivacaine 0.075% infusion. The normal-to-normal intervals (NN-interval) were downloaded from an ECG holter. Another 20 pregnant women in non-anesthesia labor (average gestation age was 38.6 weeks) were included in the comparison group. In this study, HHT was used to decompose components of ECG signals, which reflect three different frequency bands of a person's heart rate spectrum (viz. high frequency (HF), low frequency (LF) and very low frequency (VLF)). It was found that the change of energy in subjects without anesthesia was more active than that with continuous epidural bupivacaine 0.075% infusion. The energy values of the experimental group (i.e., labor analgesia) of HF and LF of ANS activities were significantly lower (<i>P</i> < 0.05) than the values of the comparison group (viz. labor without analgesia), but the trend of energy ratio of LF/HF was opposite. In conclusion, the sympathetic and parasympathetic components of ANS are all suppressed by continuous low-dose epidural bupivacaine 0.075% infusion, but parasympathetic power is suppressed more than sympathetic power.

Highlights

Epidural analgesia is commonly used for pain relief during labor in modern obstetric practice, but the influence on the fetus and childbirth are still called into question
Our result indicates that the high frequency heart rate under the effect of parasympathetic tone was lowered by the anesthesia
According to previous studies [15,16,17], the low/high frequency energy ratio reflects the index of sympathy-vagal balance, which means the sympathetic and parasympathetic components of autonomic nervous system (ANS) are all suppressed by continuous low-dose epidural bupivacaine 0.075% infusion, but the parasympathetic power is suppressed more than the sympathetic power

Summary

Introduction

Epidural analgesia is commonly used for pain relief during labor in modern obstetric practice, but the influence on the fetus and childbirth are still called into question. Epidural analgesia can prolong the course of labor and increase the rate of instrument delivery. Investigation of the Effects of Continuous Low-Dose Epidural Analgesia on the Autonomic Nervous System Using Hilbert Huang Transform ric indices of uterine vascular resistance significantly increased 1, 2, and 4 hours after epidural infusion, and returned to the baseline (before analgesia) after delivery. Sympathovagal effects and the ANS response were assessed in women in labor under epidural or spinal anesthesia, which can be treated by heart rate variability analysis [2, 5, 6]. Traditional assessments of ANS activity and sympathovagal effects are based on the assumption of linearity, while human cardiac system performs as a nonlinear system. This work presents a new assessment of ANS activity based on an innovative technique for a nonlinear system

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