Age-Related Influences of Leg Vein Filling and Emptying on Blood Volume Redistribution and Sympathetic Reflex during Lower Body Negative Pressure in Humans.

Abstract

In aged people, decreases in stroke volume and cardiac output during orthostatic challenge were found to be reduced [1][2][3]. Although the exact mechanisms have not been well clarified, it is supposed that the stiffness of the vessels is greater in the elderly, blunting venous pooling in the legs and reducing the drop in central blood volume in an upright position [4].Olsen et al. [5] observed that baseline leg venous compliance was smaller, and the capacitance response in the legs to lower body negative pressure (LBNP) was lower in elderly people. They proposed that the decreased leg venous compliance with advancing age and the concomitant reduction in capacitance response during LBNP could have implications for both the sympathetic reflex and the cardiovascular responses during acute hypovolemic circulatory stress, which might be diminished in aged people. Their recent study suggested that the attenuated cardiovascular responsiveness found in the elderly during orthostasis seemed to be caused by a reduction in leg capacitance response and a concomitant smaller central hypovolemic stimulus rather than a reduced efficiency of the reflex response [6]. However, no work has been done to investigate simultaneously the venous system, Japanese Journal of Physiology, 52, 77-84, 2002 Key words: venous distensibility index, half-emptying time, muscle sympathetic nerve activity, gravitational stress. Abstract:To test the hypothesis that leg vein filling and emptying functions could be impaired with advancing age, which would produce less blood volume redistribution toward the lower body and smaller sympathetic reflex response during mild gravitational stress, 9 young and 10 elderly healthy males were exposed to a lower body negative pressure (LBNP) of 15 mmHg. Venous occlusion plethysmography was used to determine the functions of the leg veins. We found that the baseline venous distensibility index (VDI) was lower (0.057Ϯ0.004 vs. 0.048Ϯ 0.003 ml · 1 00 ml, young vs. elderly; pϽ0.05), and half-emptying time (T 1/2 ) was shorter (1.6Ϯ0.1 vs. 1.3Ϯ0.1 s, young vs. elderly; pϽ0.05) in the elderly. At 15 mmHg-LBNP, VDI was decreased and T 1/2 was shortened significantly in the young group, but only slightly in the elderly group. Neither blood pressure nor heart rate changed significantly in either group. The reduction in peripheral venous pressure, which was recorded from the left antecubital vein at the cubital fossa, was less in the elderly, indicating a smaller decrease in central blood volume during LBNP; however, the enhancement of muscle sympathetic nerve activity was nearly the same as that in the young. We conclude that leg vein filling and emptying functions are impaired in elderly people, producing less blood pooling in the legs and smaller reduction in peripheral venous pressure during LBNP; the maintained sympathetic reflex response might be attributable to the well-preserved baroreflex function control of sympathetic outflow to the muscle in the elderly.

Influence of acute alcohol ingestion on sympathetic neural responses to orthostatic stress in humans

“…However, the mechanism underlying the alcohol-mediated impairment of both arterial blood pressure and forearm vasoconstriction was not determined. Increases in MSNA during LBNP occur primarily through a baroreflex response (26), and peripheral vasoconstriction is often related to the extent of MSNA activation (8,15). The present study once again demonstrated that alcohol elicited a blunted arterial blood pressure response and impaired forearm vasoconstriction during orthostatic stress, but these attenuated responses were not associated with concurrent re- Fig.…”

“…Progressive LBNP typically results in an increase in muscle sympathetic nerve activity (MSNA), which induces peripheral vasoconstriction to help maintain arterial blood pressure and prevent orthostatic hypotension (8,15,26). Narkiewicz et al (19) reported a reduction of arterial blood pressure during LBNP after alcohol but not placebo.…”

Altered venous capacitance as a cause of postprandial hypotension in multiple system atrophy

“…PPH is a phenomenon which changes in minutes, so the measurement of venous compliance is difficult in PPH. We therefore substituted calf venous capacitance (CVC) for venous compliance [3], assessing its involvement in the pathophysiology of PPH.…”

Relationship Between Vascular and Physical Function in Individuals with Peripheral Neuropathy

“…In addition, it is important to consider the changes in the structure and function of the vasculature and peripheral nerves as a result of the aging process. In that regard, Fu et al [24] reported an age-related decline in venous filling and emptying. It is not known if the progression of peripheral neuropathy may accelerate the decline in venous function, or if a decrease in venous function contributes to the progression of the disease.…”

“…In regards to venous circulation, several investigators have reported a reduction in venous function with advancing age [24] and in patients with heart failure [25]. It is not clear what mechanisms are involved in this reduced function, but impaired muscle activation and generalized deconditioning may be involved.…”