Abstract
Effects of nifedipine, the most potent Ca-antagonist used for management of hypertensive emergencies, on cerebral hemodynamics in CVDs were investigated by the Ar inhalation method. A single oral dose of 10 mg of nifedipine reduced mean arterial blood pressure (MAP) from 130 ± 20 mmHg to 119 ± 22 mmHg (p<0.05) in 8 cases of acute cerebral hemorrhage and from 108 ± 32 mmHg to 90 + 20 mmHg (p<0.05) in 5 cases of chronic ischemic cerebrovascular diseases, respectively. However, no significant changes of CBF and CMRO2 were observed in both groups. The changes of CBF had no relationship with dysautoregulation of cerebral circulation confirmed by lowering cerebral perfudion pressure by head tilting. Nifedipine also reduced peripheral vascular resistance measured in 5 cases, while cerebral resistance remained unchanged in these patients before and after administration of the drug. In a single case of thalamic hemorrhage, intraventricular pressure (IPV) was monitored, and a gradual increase of IVP from 9 mmHg to 19 mmHg was observed 45 minutes after administration of the drug. In 2 cases, therefore, effects of nifedipine on cerebral circulation with and without a simultaneous intravenous administration of glycerol (10%, 200 ml) were compared, and marked increases of CBF were observed by combined administrations of nifedipine and glycerol.
These findings suggest that nifedipine has a direct dilatatory effect on cerebral vessels, but that CBF remained unchanged possibly due to elevation of intracranial pressure caused by cerebral vasodilation or the differences of vascular susceptibilities to Ca-antagonists.
