Maternal and fetal effects of intravenous patient-controlled fentanyl analgesia during labour in a thrombocytopenic parturient

The use of intravenous (i.v.) patient-controlled fentanyl analgesia during labour in a parturient with unexplained thrombocytopenia (70 x 10(3).ml-1) is described. The patient self-administered boluses of 25 micrograms of fentanyl with a lock-out interval of ten min. In addition, a concurrent fentanyl infusion of 25 micrograms.hr-1 was given. Effective analgesia was achieved during labour and a total of 1025 micrograms of fentanyl was infused over 11 hr 55 min until delivery of a vigorous infant with Apgar scores of 9 after one and five min. Respiratory depression or undue sedation were not observed in the mother either during labour or in the post-partum period. At birth, maternal total plasma fentanyl concentration was 1.11 ng.ml-1, whereas neonatal umbilical total plasma fentanyl concentration was 0.43 ng.ml-1. Newborn plasma protein binding of fentanyl was lower compared to the mother (63% vs 89%). Thus, free fentanyl concentrations (0.16 ng.ml-1) were identical in the mother and newborn at delivery.