Nifedipine or verapamil counteracts hypertension in gravid ewes.

Hypertension frequently complicates endotracheal intubation in the severely preeclamptic parturient. The calcium entry-blocking drugs nifedipine (N) and verapamil (V) are effective antihypertensive agents in nonpregnant patients. The authors studied the maternal and fetal hemodynamic effects of these drugs in chronically instrumented gravid ewes made hypertensive with an infusion of norepinephrine (NE). Initially NE was infused to increase maternal mean arterial pressure (MAP) by 20%. The NE infusion was continued and either N, 2 mg, or V, 10 mg, was administered intravenously. MAP decreased promptly to control values following both drugs. Maternal heart rate (MHR) decreased significantly following NE infusion. MHR returned to control values following V administration, and increased significantly above control following N administration. Uterine blood flow decreased 50-60% during NE infusion, and there was no further change following either N or V. Fetal hemodynamics were unchanged throughout the study. These results suggest that both N and V may be effective antihypertensive agents in the parturient. V did not produce maternal tachycardia and may be the preferable drug.