Role of intravenous nitroglycerin in the treatment of severe pregnancy-induced hypertension complicated by pulmonary edema.

Intravenous nitroglycerin would appear to be an ideal agent for the treatment of severe pregnancy-induced hypertension complicated by cardiogenic pulmonary edema. Nitroglycerin infusion effectively reduces preload by venous dilatation and, at higher doses, results in arterial vasodilatation. Because of these pharmacologic properties, the effects of intravenous nitroglycerin were studied in three patients with severe pregnancy-induced hypertension complicated by pulmonary edema. The major cardiovascular effects of nitroglycerin were to reduce the mean pulmonary capillary wedge pressure from 27 +/- 4 to 14 +/- 6 mm Hg, which result in a change in the colloid osmotic pressure to pulmonary capillary wedge pressure gradient from -10 to 2 mm Hg. No significant changes occurred in heart rate, central venous pressure, or cardiac index. Analysis of oxygen-related parameters revealed a significant (p less than 0.05) increase in oxygen delivery and extraction accompanied by a 53% increase in oxygen consumption. The changes in oxygen-related variables appeared to be secondary to a fall in mixed venous oxygen tension from 39 +/- 4 to 33 +/- 1 torr. These changes occurred without any significant improvement in arterial oxygen tension. We conclude that while intravenous nitroglycerin expeditiously corrects the hydrostatic derangements of pulmonary edema seen in pregnancy-induced hypertension, a rapid improvement in arterial oxygenation does not occur.