Autonomic nervous system response to epidural analgesia in laboring patients by wavelet transform of heart rate and blood pressure variability.
BACKGROUND
Epidurals are effective in relieving labor pain but result in a sympathectomy that may compromise maternal hemodynamic stability and fetal perfusion. Decreases in blood pressure and heart rate can be corrected, but markers of autonomic activity would be useful to predict and prevent such changes. The goal of this study was to find markers describing the changes in autonomic nervous system activity with epidural anesthesia in laboring patients.


METHODS
The authors analyzed heart rate variability and blood pressure variability in 13 laboring patients using wavelet transform, a time-frequency analysis that accommodates rapid changes in autonomic activity. Heart rate and blood pressure variability were obtained 5 min before and 10 min after injection of 20 ml bupivacaine, 0.125%, and 50 microg fentanyl in the epidural space.


RESULTS
Blood pressure and heart rate were not affected by epidural analgesia. However, high-frequency power of heart rate variability increased after epidural (increase in parasympathetic drive). The ratio of low-frequency:high-frequency power of heart rate variability decreased. High- and low-frequency power of blood pressure variability decreased (decrease in sympathetic outflow).


CONCLUSIONS
Indices of parasympathetic and sympathetic activity after neuraxial blockade in laboring patients can be obtained by analysis of both heart rate variability and blood pressure variability. The analysis by wavelet transform can discern changes in autonomic activity when values of blood pressure and heart rate do not vary significantly. Whether this technique could be used to predict and prevent hemodynamic compromise after neuraxial blockade merits further studies.
Deschamps
Alain
A
Department of Anesthesiology, McGill University Health Centre, Royal Victoria Hospital, Quebec, Canada. alain.deschamps@staff.mcgill.ca
Kaufman
Ian
I
Backman
Steven B
SB
Plourde
Gilles
G
D000328:Adult; D015360:Analgesia, Epidural / Q000009:adverse effects*; D016362:Analgesia, Obstetrical / Q000009:adverse effects*; D001341:Autonomic Nervous System / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects*; D003627:Data Interpretation, Statistical; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D016343:Monitoring, Intraoperative; D010275:Parasympathetic Nervous System / Q000187:drug effects / Q000502:physiology; D011247:Pregnancy; D015656:Respiratory Mechanics / Q000502:physiology; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology