Atropine and glycopyrrolate: hemodynamic effects and placental transfer in the pregnant ewe

Atropine administration in pregnant women may cause fetal tachycardia and a decrease in beat-to-beat variability of the fetal heart rate. In the present study, placental transfer and maternal and fetal hemodynamic effects of atropine and glycopyrrolate were compared in chronically and in acutely instrumented, unanesthetized pregnant ewes. Administration of either atropine (0.05 mg/kg) or glycopyrrolate (0.025 mg/kg) increased maternal heart rate by 25% without changing maternal arterial pressure, fetal arterial pressure, fetal heart rate, or beat-to-beat variability. Maternal and fetal blood gas tensions also did not change. Placental transfer or atropine was significantly greater than that of glycopyrrolate throughout the entire experimental period. The peak fetal/maternal ratios observed 4 hours after injection were 1.0 for atropine and 0.13 for glycopyrrolate. On the basis of placental transfer data only, it is possible to postulate that the use of glycopyrrolate may be preferable to atropine. However, in view of the absence of circulatory effects in the fetal lamb after either atropine or glycopyrrolate, it was concluded that neither agent is preferable to the other insofar as fetal effects are concerned during ovine pregnancy. Whether these conclusions can be applied to human pregnancy remains to be determined.