The effect of isosorbide dinitrate on placental blood flow and maternal blood pressure in women with pregnancy induced hypertension

Abstract

The effect of isosorbide dinitrate (ISDN) on maternal and fetal circulation was assessed in 23 women with pregnancy induced hypertension (PIH). A double-blind randomized design was employed. Each woman was given a sublingual tablet of ISDN (5 mg) or placebo. Maternal blood pressure (BP) and heart rate (HR) were measured before and every 2 min after the medication or placebo, for a total of 20 min. Flow velocity waveforms in the uterine and umbilical arteries were recorded at the same time periods, using pulsed Doppler ultrasound. The ratio of peak systolic to end-diastolic flow velocity (S/D) in those vessels was calculated. After ISDN mean maternal BP fell from 103 +/- 1.8 mm Hg to 90.5 +/- 2.9 mm Hg at 14 min (P < .0001) and mean maternal HR increased from 97.3 +/- 3.8 beats/min to 115.7 +/- 3.5 beats/min at 12 min (P < .0001). The mean S/D in the umbilical artery fell from 3.07 +/- 0.33 to 2.58 +/- 0.23 at 8 min (P < .0007). The mean S/D in the uterine artery fell from 3.27 +/- 0.6 to 2.38 +/- 0.28 at 10 min (P < .0001). In seven of 12 women with an early diastolic notch in the uterine artery flow velocity waveform the notch diminished or disappeared within the first 6 min after the medication. No significant change in any of the measured parameters was observed in the placebo group. Our finding that ISDN altered maternal and fetal hemodynamics in PIH lends support to the further exploration of nitric oxide donors in the treatment and prevention of pregnancy induced hypertension.