Hemodynamic changes during dietary salt loading in elderly patients with essential hypertension

Hemodynamic changes with dietary salt loading were assessed by Doppler echocardiography during different sodium intake (7 g/day for 8 weeks, 20 g/day for 1 week) in 29 elderly patients with essential hypertension (81.6 +/- 6.7 years, 4 men, 25 women). With salt loading, 24 patients whose mean blood pressure (MBP) increased by 10% or more were defined as salt sensitive (SS) group, and 5 patients whose MBP did not change, or increased by less than 10% were defined as non-salt sensitive (NSS) group. Based on the mitral flow velocity integral, cardiac output (CO) was calculated, and total peripheral resistance (TPR) was calculated as MBP divided by CO. Nine of the 24 SS patients were termed "SS (COdep)" whose CO increased significantly with salt loading. In the remaining 15 SS patients termed "SS (TPRdep)", TPR increased significantly with sodium repletion. Blood flow in the common carotid, superior mesenteric, or terminal aorta was calculated from each flow velocity integral. The percent change in peripheral resistance calculated by dividing MBP by each blood flow was obtained. There were no significant percent changes in the common carotid resistance in SS (COdep), SS (TPRdep) or NSS groups. The superior mesenteric resistance increased significantly in all three groups. The terminal aortic resistance increased in the SS (TPRdep) group, but decreased in the SS (COdep) or NSS group. These results indicate that salt sensitivity is ascribable to changes in regional vascular resistances.