The effects of sodium depletion on ambulatory blood pressure and heart rate monitoring in the elderly

Abstract

Objective: Old age is associated with impairment of the normal homeostatic response to cardiovascular stress. The purpose of our study was to determine whether a physiologic stress, such as sodium depletion, produces different, age-dependent effects on the blood pressure and heart rate profile in old and young subjects.

Design: Blood pressure and the heart rate were studied in 11 young (age 28.7 +/- 3.1 years) and 14 elderly (76.1 +/- 3.4 years) male healthy volunteers, during ambulatory blood pressure monitoring and during postural stress before and after 2 days of sodium depletion.

Methods: Twenty-four-hour blood pressure monitoring was performed with a non-invasive automatic portable monitoring device. The postural evaluation consisted of a standard passive upright-tilt test to 70 degrees. Sodium depletion was obtained with a low-salt diet and diuretic treatment (100 mg hydrochlorothiazide) for 2 days.

Results: After sodium depletion no changes were found in the average blood pressure. The postural evaluation showed a fall in systolic blood pressure only in the elderly. The heart rate increased only in the young group, both during the ambulatory blood pressure monitoring and after the upright tilt.

Conclusions: These results suggest that cardiovascular reserve is decreased in the elderly under a stress condition such as sodium depletion; this phenomenon may be linked to a blunted baroreceptor reflex response.