Case Presentation: This is the case of an ex-41 2/7 week baby girl, born to a 28 year old G4P0 now 1 mother via cesarean section for arrest of descent. Early in pregnancy, the mother endorsed occasional marijuana use and had one urine toxicology screen positive for marijuana. Subsequent urine drug screens were all negative, including one done 7 hours prior to delivery. Per protocol, due to the history of substance use, urine and meconium toxicology screens were run on the first void and stool of the newborn. The urine test came back positive for Fentanyl, while the meconium drug screen was negative. The only medications administered to the infant prior to the samples were intramuscular vitamin K and ophthalmic erythromycin. Prior to delivery, the mother received prenatal vitamins (her only home medication) and per the medical record, intra-thecal Morphine, Oxytocin, Bicitra, Diphenhydramine, and Penicillin G.
Discussion: The discrepancy in urine drug screen results between mother and baby pose a clinical conundrum for practitioners. Hospital policy states that an unexplained positive drug screen for an opioid in a newborn warrants a 5-day hold for withdrawal monitoring. Breastfeeding is often discouraged in these cases, and there is a social work consult and potential child protective services involvement. All of this is extremely disruptive to the family dynamic, and also increases the cost of the hospital stay. Additionally, social services in most parts of the country are already overburdened due to the opioid crisis and other reasons.
Although there is some Anesthesia literature to show that Fentanyl given in the intra-thecal space via epidural ends up in maternal serum, many anesthesiologists maintain that Fentanyl from an epidural should not be detectable in the newborn. This is despite Fentanyl being known to cross the placenta. Further complicating the matter, depending on the electronic medical record (EMR) used, Anesthesiologists may be documenting in a separate section, making it unclear which mothers are getting Fentanyl in their epidurals in the first place. After review of the literature we found only one single published case report of a positive urine drug screen in a neonate after intra-thecal Fentanyl was administered during labor and delivery.
Another possibility is a false positive due to cross-reactivity with other substances. Wang et. all conducted a study to examine which medications and metabolites can cause a false positive for Fentanyl in a urine drug screen. Out of 1,269 consecutive urine drug screens 36 were positive for Fentanyl, but after confirmatory testing they found that 5 of the 7 samples were false positive. This was thought to be due to Risperidone and 9-hydroxyrisperidone.
Conclusions: Fentanyl is increasingly being used as a drug of abuse. Many hospitals have responded by adding it to the substances tested for in urine drug screening. While appropriate to screen newborns for drugs of abuse, the frequency of Fentanyl use in epidurals complicates a positive result in the urine tox, especially when the results between mom and baby are discrepant. As pediatric hospital medicine expands to include more and more newborn nursery care, we will be leaders in delineating the limitations of the laboratory studies available to us. The psychological stress to families, increased hospital costs and ethical turmoil this causes patient care teams needs to be acknowledged and addressed in order to improve patient care.