Quantification of serum fentanyl concentrations from umbilical cord blood during Ex utero intrapartum therapy

Fetal IM injection of fentanyl is frequently performed during ex utero intrapartum therapy (EXIT procedure). We quantified the concentration of fentanyl in umbilical vein blood. Thirteen samples from 13 subjects were analyzed. Medians and ranges are reported as follows. Weight of the newborn at delivery was 3000 g (2020-3715 g). The dose of fentanyl was 60 μg (45-65 μg). The time between IM administration of fentanyl and collection of the sample was 37 minutes (5-86 minutes). Fentanyl was detected in all of the samples, with a median serum concentration of 14.0 ng/mL (4.3-64.0 ng/mL).