HEMODYNAMIC EFFECTS AND PLACENTAL TRANSFER AFTER CONTINUOUS INTRAVENOUS APPLICATION OF REMIFENTANIL IN THE CHRONIC MATERNAL-FETAL SHEEP PREPARATION

Abstract

S252 Remifentanil is a new ultrashort-acting anilidopiperidine with a [micro sign]-specific opioid action. Remifentanil with its unique properties could be of particular use for fetal and maternal analgesia during fetal surgery. However, the hemodynamic changes and pharmacokinetic behavior of remifentanil in the pregnant patient have not been studied in depth. METHODS: Using the chronic maternal-fetal sheep preparation, a continuous infusion of remifentanil 0.33 [micro sign]g/kg/min was administered intravenously over 60 min. Fetal and maternal arterial blood samples were obtained for remifentanil levels before and at 5, 15, 30, 60, 65, 75 and 120 min following start of the infusion. At regular intervals, arterial blood samples were drawn to determine blood gases and acid-base status of mother and fetus. Maternal mean arterial pressure (MMAP), uterine bloodflow (UBF), maternal heart rate (MHR), fetal mean arterial pressure (FMAP) and fetal heart rate (FHR) were recorded continuously. Statistical analyses were performed using repeated measures of ANOVA followed by Dunnett t-testing. A p value < 0.05 was considered significant. RESULTS: Eight experiments were performed in eight ewes. MMAP, MHR FHR, FMAP and UBF or blood-gases and acid-base status in mother or fetus did not change significantly during remifentanil infusion. Peak levels of remifentanil were detected in maternal plasma after 30 min. and reached 3.5 ng/ml. Peak fetal plasma levels of 0.36 ng/ml were attained after 60 min. (Figure 1)Figure 1CONCLUSION: This study indicates that intravenous aplication of remifentanil has not any significant effect on maternal and fetal cardiovascular and acid-base status in the pregnant ewe. Peak fetal plasma concentration of remifentanil reached 14% of the peak maternal placental concentration.