The effect of lumbar epidural anesthesia on fetal heart rate baseline variability.

Baseline fetal heart rate (FHR) variability has become an important parameter in the diagnosis of fetal distress when electronically monitoring the fetus. Loss of the baseline variability has been noted to be associated with fetal distress, and in association with late deceleration or severe variable deceleration patterns has been shown to be ominous. Baseline FHR variability, however, has been modified not only by fetal distress but also by prematurity and the administration of certain drugs to the mother. Because FHR is often monitored during labor in parturients given lumbar anesthesia, the question of the effect of this procedure on FHR variability arose. Fifteen such patients with no antepartum or intrapartum complications were studied in active labor. All were monitored by electrocardiography on a continuous basis, FHR being studied before and after epidural anesthesia with lidocaine, with and without epinephrine. Of the 15 patients, tracings in 8 (53 percent) revealed a minimal or moderate change in baseline variability within several minutes of drug injection. This change in variability was recorded from 4 to 18 minutes, after which time the pre-epidural FHR variability was reestablished. Although the mechanism for this result was not definitively determined, such variability in FHR does not in itself seem significant of fetal distress but suggests supportive measures for the patient.