RESEARCH: Ageing and water homeostasis.

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Novartis Found Symp 2002;242:265-75; discussion 275-8

Ageing and water homeostasis.

on D, Jordan J, G, Ketch T, JR, Biaggioni I.

Autonomic Dysfunction Center, Department of Medicine, Vanderbilt University,

Nashville TN 37232 2195, USA.

This review outlines current knowledge concerning fluid intake and volume

homeostasis in ageing. The physiology of vasopressin is summarized. Studies

have been carried out to determine orthostatic changes in plasma volume and

to assess the effect of water ingestion in normal subjects, elderly

subjects, and patients with dysautonomias. About 14% of plasma volume shifts

out of the vasculature within 30 minutes of upright posture. Oral ingestion

of water raises blood pressure in individuals with impaired autonomic

reflexes and is an important source of noise in blood pressure trials in the

elderly. On the average, oral ingestion of 16 ounces (473ml) of water raises

blood pressure 11 mmHg in elderly normal subjects. In patients with

autonomic impairment, such as multiple system atrophy, strikingly

exaggerated pressor effects of water have been seen with blood pressure

elevations greater than 75 mmHg not at all uncommon. Ingestion of water is a

major determinant of blood pressure in the elderly population. Volume

homeostasis is importantly affected by posture and large changes in plasma

volume may occur within 30 minutes when upright posture is assumed.

PMID: 11855693 [PubMed - in process]