TREATMENT OF EXCESSIVE POLYCYTHEMIA OF HIGH-ALTITUDE WITH RESPIRATORY STIMULANT-DRUGS

Abstract

Excessive polycythemia of high altitude is characterized by excessive hypoxemia due, in part, to hypoventilation. Because progestational agents have stimulant effects on ventilation, the effect of medroxyprogesterone acetate was evaluated on 17 patients with excessive polycythemia of high altitude residing at an altidued of 3100 m. After 10 wk of therapy with 20 mg of medroxyprogesterone acetate 3 times/day, the mean .+-. SE hematocrit decreased in all 17 patients from 60.1 .+-. 1.6 to 52.1 .+-. 1.5% (P .+-. < 0.001). Mean resting ventilation increased on medroxyprogesterone acetate from 9.7 .+-. 0.48 to 11.7 .+-. 0.32 l/min (P < 0.001) due to an increase in tidal volume with no systematic effect on breathing frequency. This decreased the ratio of dead space to tidal volume from 42.1 .+-. 1.6 to 35.7 .+-. 2.1% (P < 0.01). The arterial PCO2 [partial pressure of CO2] decreased 4.3 mm Hg on medroxyprogesterone acetate from 32.9 .+-. 0.8 to 28.6 .+-. 0.8 mm Hg (P < 0.001); the normal arterial PCO2 at an altitude of 3100 m is 30.9 .+-. 0.9 mm Hg. The arterial PO2 [partial pressure of O2] increased 3.1 mm Hg, from 44.0 .+-. 1.7 to 47.1 .+-. 1.5 mm Hg (P < 0.01); the normal value is 54 .+-. 1 mm Hg). The O2 saturation increased from 83.9 .+-. 1.1 to 89.6 .+-. 0.9%. No change in ventilatory response to CO2 occurred with medroxyprogesterone acetate. Hypoxic ventilatory response increased significantly only in the patients with normal lungs. During 16 mo. of treatment with medroxyprogesterone acetate, the decrease in hematocrit was sustained in all but 1 of 15 patients. Medroxyprogesterone acetate is an effective form of therapy in excessive polycythemia of high altitude because of its effects on ventilation and tidal volume, and the resultant increase in arterial O2 saturation.