Metoclopramide exaggerates stress-induced tachycardia in pregnant sheep

Metoclopramide is often administered to hasten gastric emptying prior to cesarean section and during labor, but has also been demonstrated to increase catecholamine release during stress and to increase heart rate and blood pressure in nonpregnant humans. The purpose of this study was to examine the maternal and fetal effects of metoclopramide during maternal stress in pregnant ewes. After baseline measures, eight ewes were randomly allocated to receive either intravenous metoclopramide, 10 mg, or saline, followed in 10 min by nonpainful stress to increase mean arterial pressure 40%-45% for 30 s. At least 2 days later, the ewes received the alternate treatment. Metoclopramide, but not saline, increased resting maternal heart rate. In the 10 min after maternal stress, maternal heart rate was increased more after metoclopramide than after saline treatment, whereas maternal blood pressure, uterine blood flow, and fetal hemodynamic variables and arterial blood gas tensions did not differ between the two treatments. Whereas these results are not consistent with a generalized increase in sympathetic nervous system tone after a single dose of metoclopramide, they do suggest that metoclopramide may exaggerate tachycardia after stress, encountered frequently both during and after cesarean section.