Ritodrine hydrochloride induced cardiopulmonary and placental hemodynamic changes in normal and hypertensive late pregnancy.

Cardiopulmonary parameters (minute volume, heart rate, stroke volume, right heart, pulmonary and left heart blood volumes), blood pressure and placental blood flow were evaluated in 20 normal patients, nine patients with preeclamptic disease and 12 with essential hypertension in late pregnancy before and 60 minutes after a single i.m. dose of 10 mg of ritodrine hydrochloride. The drug caused a statistically significant increase in heart rate in all the patient groups, while the systolic and diastolic blood pressures were only slightly affected. Minute volume was unchanged in the group of normal patients, but in both hypertensive groups there was a significant increase. The placental perfusion index was statistically nearly significantly decreased in the group of uncomplicated pregnancies, statistically significantly increased in preeclamptic patients, and not affected in the group with essential hypertension. Ritodrine hydrochloride medication can be expected to have a positive effect on placental blood flow only in preeclamptic disease, and then probably in the milder forms of the disease.