The effects of intravenous and epidural sufentanil in the chronic maternal-fetal sheep preparation.

This study examines the placental transfer and hemodynamic and acid-base changes after intravenous (i.v.) and epidural administration of sufentanil in the chronically instrumented maternal-fetal sheep preparation. A dose of 50 micrograms sufentanil was injected either i.v. or epidurally into seven ewes. Neither i.v. nor epidural injection of sufentanil affected maternal mean arterial pressure (MMAP), uterine blood flow (UBF), maternal heart rate (MHR), fetal mean arterial pressure (FMAP), fetal heart rate (FHR), or blood gases and acid-base status in mother and fetus, After i.v. administration, a peak sufentanil level of 1.28 ng/mL +/- 0.285 (SD) was detected in maternal plasma. A peak plasma level of 0.037 ng/mL +/- 0.041 (SD) was attained in the fetus. A constant maternal-fetal concentration ratio of 5.5 from 15-60 min after the i.v. injection was found. After epidural injection a mean peak plasma level of 0.059 ng/mL +/- 0.042 (SD) was reached in the mother 25 min after injection. Sufentanil levels were undetectable in fetal plasma after epidural injection into the mother. Because placental transfer of sufentanil is small, the maternal and fetal cardiovascular and acid-base effects are minimal in the pregnant ewe.