Abstract
Dear Editor:
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The patient gave consent, and the research ethics board gave approval for this study. A 34-year-old, 39-week gravida 1 para 0 woman presented in spontaneous labor. She was 162 cm tall, weighed 75 kg, was healthy, took no medication other than prenatal vitamins, and had enjoyed an uneventful pregnancy. She requested and received an epidural at 4:45 h the day of her admission. The epidural catheter placement was uncomplicated, and adequate analgesia was provided using a pump that infused 0.06% bupivacaine with 2 μg/mL fentanyl at 10 mL/hour with a patient-controlled 5-mL demand bolus and a lockout time of 10 minutes. Throughout her labor the patient received six extra boluses of this solution.
A 3,780-g baby boy was born at 14:08 h, with Apgar scores of 9 and 9 at 1 and 5 minutes, respectively, and an umbilical artery pH of 7.19. The epidural pump was stopped soon after birth, with the patient receiving 140 mL of the epidural solution (280 μg of fentanyl over 11 hours = 25 μg/hour). The patient recovered and was discharged to the postpartum ward where she was assessed by us the next day. At that time she had used no medications for pain.
The baby-dependent items on the LATCH score were assessed, and the latching ability and audible swallowing were rated at 2 (normal). Urine samples were collected from the mother at 14:00 h. At the same time, a clean sponge was placed in a new diaper, which provided a neonatal urine sample that was collected at 17:00 h. The samples were sent to a toxicology laboratory, where it was determined that the maternal urinary fentanyl level was 2.0 ng/mL, whereas the neonatal level was 2.4 ng/mL.
Although it is known that epidurally administered fentanyl crosses the placenta, it is thought that this leads to clinically unimportant levels in the neonate. 2 The measured half-life of fentanyl administered intravenously to infants 1 day or less of age is highly variable and ranges from 75 to 441 minutes, 3 making the duration it would remain in the neonate unclear. Our case demonstrates that fentanyl can persist in the neonate for at least 24 hours after delivery, at amounts that may have clinical effects. The minimum effective analgesic level of fentanyl in plasma for adults is 0.63 ng/mL. 4 Although the corresponding level is unknown in neonates, a level of 1.1 ng/mL has necessitated prolonged intubation in neonates. 3 The urinary concentration seems to have some correlation with fentanyl dosage and levels. 5
Although fentanyl is transferred in breastmilk, it is virtually undetectable in colostrum 10 hours after it has been given maternally. 6 In addition, fentanyl's limited oral bioavailability makes us believe the majority of neonatal fentanyl was from placental transfer and not through breastmilk. Although our LATCH score was reported as normal, more subtle markers of breastfeeding difficulty may have been found if we had assessed the Widstrom stages of neonatal breastfeeding, 7 or more severe problems may have occurred if the patient had required higher fentanyl doses. Adequate initiation is essential for the continued success of breastfeeding, and it is possible that the presence of neonatal fentanyl could interfere in the important first days of life.
In conclusion, we provide evidence that fentanyl administered through an epidural for less than 12 hours will remain in the mother and neonate, even 24 hours after cessation of the epidural infusion. The clinical implications of this should be further investigated.