Maternal and neonatal side-effects of remifentanil patient-controlled analgesia in labour

Background. Remifentanil has been suggested as an ideal opioidfor patient-controlled analgesia (PCA) in labour, but the safetyprofile has not been established. The aims of this preliminaryprospective observational study were to investigate the maternalside-effects and early neonatal effects, and to assess the placentaltransfer of remifentanil PCA during labour. Methods. Women with no known obstetric complications or contraindicationto remifentanil were recruited (n=50). Remifentanil was administeredat a bolus dose of 0.5 µg kg^–1 and a lockout periodof 2 min. A visual analogue scale was used to assess pain, nauseaand itching. Maternal observations were recorded hourly andfetal heart rate trace was assessed every 2 h. Umbilical cordgases, 1 and 5 min Apgar scores and neurological evaluationof the neonate were recorded. Maternal venous blood and umbilicalartery and vein cord blood samples were collected for analysisof remifentanil concentration. Results. Fifty women enrolled in the study (24 multiparous,26 primiparous). There was no evidence of cardiovascular instabilityor respiratory depression. Pain scores decreased significantly,but there was no significant change in nausea after initiatingthe PCA. A statistically significant increase in itching wasfound to be clinically mild and 22 women were slightly drowsy(95% confidence interval CI], 30–58.7%) but alert tovoice. Ten fetal heart rate traces demonstrated changes in thefirst 20 min, but did not require intervention (95% CI, 10–33.7%).The median 1 and 5 min Apgar scores were 9. The mean umbilicalcord gases and neurological examination were within normal limits.Maternal vein and umbilical vein cord samples demonstrated placentaltransfer of remifentanil, and small amounts were detected inumbilical artery samples. Conclusions. At the bolus dose used remifentanil PCA has anacceptable level of maternal side-effects and minimal effecton the neonate. Remifentanil crosses the placenta and appearsto be either rapidly metabolized or redistributed in the neonate.