Long-term effects of hydralazine on ventilation and blood gas values in patients with chronic obstructive pulmonary disease and pulmonary hypertension

Abstract

Hydralazine has been shown to increase minute ventilation, alveolar ventilation, and arterial partial pressure of oxygen (PaO 2) after short-term administration in patients with chronic obstructive pulmonary disease and pulmonary hypertension. The effects of orally administered hydralazine on ventilation and blood gas values were evaluated after six to 18 months of treatment in 10 male patients who had demonstrated an increase in minute ventilation after 24 hours of treatment. Hydralazine was administered at a dose of 200 mg per day during the initial 24 hours and in doses ranging from 40 mg per day to 200 mg per day during long-term therapy. Following 24 hours of treatment, a statistically significant increase in minute ventilation, alveolar ventilation, and PaO 2, and reduction in arterial partial pressure of carbon dixoide (PaCO 2) were seen both at rest and during exercise. After six to 18 months of hydralazine therapy, the increase in minute ventilation at rest persisted when compared with the pre-hydralazine value (15.3 ± 1.3 liters/minute versus 13.1 ± 1.1 liters/minute; p <0.05). The improvement in PaO 2 at rest continued relative to the prehydralazine value (70.9 ± 3.2 mm Hg versus 65.1 ± 3.0 mm Hg, p <0.05) as did the PaO 2 during exercise (60.3 ± 3.5 mm Hg versus 53.3 ± 2.0 mm Hg; p <0.05). The reduction in PaCO 2 at rest persisted compared with the pre-hydralazine value (41.2 ± 2.4 mm Hg versus 47.0 ± 3.0 mm Hg; p <0.05) as did the PaCO 2 during exercise (44.0 ± 2.8 mm Hg versus 48.0 ± 2.8 mm Hg; p <0.05). No significant changes in minute ventilation, PaO 2, or PaCO 2 were seen at rest or during exercise, when re-measured after six to 18 months in an age-and sex-matched control group of 10 patients who did not receive hydralazine. These results demonstrate that the short-term effects of hydralazine on ventilation and blood gas values persisted after six to 18 months of treatment in this sample of patients, some of whom received doses less than 200 mg per day.