The effects of epidural anesthesia on electronic fetal heart rate monitoring.

A variety of changes of FHR monitoring parameters have been attributed to epidural anesthesia. Epidural anesthesia with lidocaine may cause tachycardia in a small percentage of patients and decreased FHR variability in other patients. No changes in baseline FHR have been observed after epidural anesthesia with bupivacaine or chloroprocaine. Chloroprocaine causes no significant change in FHR variability. Bupivacaine is associated with a statistically significant increase in FHR variability when group data are compared. However, this response does not occur in every patient, nor is it predictable in any given patient. Several studies have shown high incidences of pathologic periodic changes in FHR in women receiving epidural anesthesia with lidocaine. These changes appear to be strongly related to both maternal hypotension secondary to anesthesia-induced sympathetic blockade and to maternal uterine hypertonus. Studies in which bupivacaine or chloroprocaine were employed, and in which hypotension was avoided, indicate that observed pathologic periodic changes are not related to drug injection but rather to sporadic nonanesthesia-induced changes in uterine activity. Epidural anesthesia employing anesthetic solutions to which epinephrine has been added lead to decreased uterine activity. Epidural anesthesia without epinephrine appears to have no effect on uterine activity. In general, epidural anesthesia in the absence of maternal hypotension or uterine hypertonus causes minimal changes in the FHR parameters. Those changes that do occur are neither universal or predictable. Therefore, any alteration in FHR monitoring parameters occurring in a patient receiving epidural anesthesia should be evaluated and acted upon in the same fashion and by the same methods one would employ if the patient were not receiving epidural anesthesia.