A comparison between the haemodynamic effects of oral nifedipine and intravenous dihydralazine in patients with severe pre-eclampsia

Abstract

To compare the effects of a single oral dose of nifedipine with those of intravenous dihydralazine on central haemodynamics in pregnant women with severe pre-eclampsia. A prospective comparative study. The High Risk Obstetric Unit, University Hospital Rotterdam Dijkzigt, Rotterdam. Twenty patients with severe pre-eclampsia between 27 and 35 weeks gestation with normal cardiac filling pressures and without fetal distress. A pulmonary artery thermodilution catheter and a radial artery line were placed. Ten patients chewed a 10-mg capsule of nifedipine and 10 patients received dihydralazine by intravenous infusion at a rate of 1-3 mg/h. Arterial pressures, heart rate, cardiac output and pulmonary capillary wedge pressure were determined before and after drug administration. Fetal condition was continuously monitored by cardiotocography. The reduction in arterial blood pressure obtained with both drugs was similar, and was associated with a similar rise in heart rate and cardiac output and a similar reduction in systemic vascular resistance. Pulmonary capillary wedge pressures decreased significantly less with nifedipine than with dihydralazine. Signs of fetal distress occurred in none of the nifedipine-treated patients, but in five of the patients treated with dihydralazine. From the haemodynamic viewpoint nifedipine seems to be a useful agent in the treatment of hypertensive emergencies in pregnancy.