Background: This randomized double-blind investigation was designed to study the placental transfer and neonatal effects of epidural sufentanil and fentanyl infused with bupivacaine for labor analgesia.
Methods: Healthy parturient women (n = 36) received epidural bupivacaine alone (group B) or with fentanyl (group B-F) or sufentanil (group B-S). Group B received a 12-ml bolus of 0.25% bupivacaine followed by a 10 ml/h infusion of 0.125% bupivacaine. Groups B-F and B-S received a 12-ml bolus of 0.125% bupivacaine with 75 micrograms fentanyl or 15 micrograms sufentanil, respectively, followed by 10 ml/h of 0.125% bupivacaine with fentanyl 1.5 micrograms/ml or sufentanil 0.25 micrograms/ml. Maternal venous (MV) and umbilical arterial (UA) and umbilical venous (UV) bupivacaine and opioid plasma concentrations were determined. Neonatal assessment included Apgar scores, umbilical cord blood gas analyses, and neurobehavioral testing at delivery and at 2 and 24 h of life using the Neurologic and Adaptive Capacity Score (NACS).
Results: The mean total dose of fentanyl was 136.6 +/- 13.1 micrograms (SEM), and of sufentanil, 23.8 +/- 1.8 micrograms. Although administered in a ratio of 5.7:1, fentanyl and sufentanil MV plasma concentrations were in the ratio of 27:1. UV/MV ratios were 0.37 for fentanyl and 0.81 for sufentanil. Fentanyl was detected in most UA samples, whereas sufentanil was present in only one sample. Neonatal condition was good and generally similar in all groups, with the exception of a lower NACS at 24 h in group B-F.
Conclusions: Although the degree of placental transfer of sufentanil appeared greater than that of fentanyl, lower MV sufentanil concentrations resulted in less fetal exposure to sufentanil. The lower NACS at 24 h in group B-F may reflect the continued presence of fentanyl in the neonate.