Comparison of nitroprusside and hydralazine in hypertensive pregnant ewes.

During phenylephrine-induced hypertension in 6 near-term pregnant ewes, nitroprusside rapidly lowered the blood pressure to control values with no accompanying change in uterine blood flow. Hydralazine slowly lowered the blood pressure to control values. This change was accompanied by a statistically significant (15%) increase in uterine blood flow. Hydralazine also had a more pronounced effect than nitroprusside on cardiac output, heart rate, and total peripheral resistance. There were no significant acid-base changes in mother or fetus throughout the study.