The effects of meperidine and epidural analgesia in labor on maternal heart rate variability

Epidural and parenteral opioid analgesia are two common methods of pain relief in labor that may influence the autonomic nervous system. However, these effects on laboring women have not yet been adequately studied. The aim of our study was to assess the effects of these two methods of analgesia on autonomic nervous system modulation of maternal heart rate variability in laboring women.

A prospective observational study was conducted on 64 laboring women; 33 received epidural analgesia with bupivacaine and fentanyl and 31 intravenous meperidine and promethazine. Power spectral analysis and nonlinear methods were applied to digitized electrocardiograms performed before and after administration of analgesia, to assess maternal heart rate variability and autonomic equilibrium.

Maternal heart rate significantly increased in women who received meperidine compared to those who had epidural analgesia. There was a significant increase in the low-frequency to high-frequency ratio (3.7+/-3.9 vs. 1.8+/-1.6, P<0.05), and a significant decrease of high-frequency spectral power in women who had meperidine compared to those who received epidural analgesia (163+/-91 vs. 98+/-100 ms(2)/Hz, P<0.05).

Meperidine caused an autonomic nervous system shift towards sympathetic activation with abolition of respiratory sinus arrhythmia high-frequency spectral band. Conversely epidural analgesia had no significant effect on autonomic nervous system control of heart rate.