Placental transfer and neonatal effects of remifentanil as an adjuvant for cesarean section

Abstract

Objective To investigate the placental transfer and neonatal effects of remifentanil as an adjuvant for cesarean section.Methods Forty ASA Ⅰ parturients at full term aged 26-32 yr weighing 70-90 kg undergoing elective cesarean section under combined spinal epidural anesthesia (CSEA) were randomly divided into 2 groups (n = 20 each): control group (C) and remifentanil group (R). The CSEA was performed at L3-4interspace and the upper spread of sensory block reached T6-8. Group R received TCI of remifentanil (target plasma concentration was set at 1.5 ng/ml) starting from performance of CSEA until blood samples were obtained. In group C equal volume of normal saline was infused instead of remifentanil. MAP, HR, RR, minute ventilation (MV), and OAA/S scores were recorded after the parturients had settled down for 5 min in the operating room (T0), at skin incision (T1), when the baby was being delivered (T2), uterus repaired (T3) and peritoneum closed (T4). Fetal heart rate (FHR) at T0 and immediately before skin disinfection, the duration between uterus incision and delivery of the baby (delivery time), body weight of the newborn, Apgar score at 1 min and 5 min after delivery and neonatal behavioral neurological assessment (NBNA) at 1 h and 24 h after delivery were also recorded.Adverse effects including hypotension, sinus bradycardia, raspiratory depression, muscle rigidity , nausea and vomiting were recorded. The middle segment of umbilical cord (about 10-15 cm long) was clamped at both ends with two clamps at delivery. Umbilical arterial (UA) and venous (UV) blood samples and maternal arterial (MA) blood samples were obtained within 3 min after delivery for blood gas analysis and determination of plasma remifentanil concentration using C,C-MS-SIM method. Results OAA/S scores were significantly lower at T1,2 in group R than in group C. There were no significant differences in MAP, HR, MY, RR, delivery time, FHR, blood gases, bedy weight of the newborn, Apgar scores and NBNA scores between the 2 groups. The plasma concentrations (C) of remifentanil were (0.85±0.31),(0.57±0.12) and (0.22±0.09) ng/ml respectively in maternal arterial, umbilical venous and arterial blood samples, CUV/CMA was 0.67±0.41 and CUA/CUV was 0.39±0.08. Conclusion Remifentanil given by TCI at a target plasma concentration of 1.5 ng/ml has no adverse effects on the newborn because of raid metabolism and redistribution of remlfentanil in the neonate after rapid placental transfer. Key words: Piperidines; Cesarean section; Infant, newborn; Placenta