Effect of nifedipine on oxygen delivery in patients with angina pectoris: relation between blood viscosity and hematocrit

Abstract

The effect of nifedipine on blood viscosity and hematocrit was investigated. Blood was sampled from eight patients with angina pectoris (mean age: 59 +/- 8 yr) treated with nifedipine (20-30 mg/day) for 5 months. Using a cone-plate type viscometer, blood viscosity was determined at the shear rates of 37.5 and 375 sec-1 at 37 degrees C. Hematocrit was also measured at the same time. Since the ratio of hematocrit to blood viscosity at a shear rate of 375 sec-1 can be considered to reflect oxygen delivery, this ratio (oxygen delivery index) was also calculated. Blood viscosity at a shear rate of 37.5 sec-1 was significantly (P less than .05) decreased by nifedipine treatment, but hematocrit and the blood viscosity at a shear rate of 375 sec-1 were not changed. The oxygen delivery index, however, was significantly (P less than .01) increased after the administration of nifedipine. These results suggest that oxygen delivery increased by the treatment with nifedipine and inhibited erythrocyte aggregation by decreasing blood viscosity at low shear rate.