Delayed recovery from initial orthostatic hypotension: an expression of frailty in the elderly

Excerpt

Initial orthostatic hypotension (OH) is a clinical syndrome with a transient drop in blood pressure upon standing (by definition > 40 mmHg systolic or > 20 mmHg diastolic within 15 sec after standing up from supine position) [1]. This is different from classic OH which is defined by a sustained reduction of at least 20 mmHg in systolic or 10 mmHg in diastolic blood pressure within 3 min of standing [2]. The pathophysiological mechanisms leading to initial OH appear to differ from classic OH, as initial OH typically occurs upon active standing and not during passive tilting. Therefore, the active use of leg and abdominal muscles appears to be involved. It has been hypothesized that muscle contraction increases venous return to the right atrium and slightly increases arterial blood pressure, especially in elderly [1, 3]. The subsequent stimulation of mechanoreceptors in the right atrium and arterial baroreceptors results in abrupt withdrawal of sympathetic activity. Immediately after this occurs, muscle contraction leads to local arterial vasodilation during the first 4 s after contraction. Together, this results in a fall in systemic vascular resistance for 6–8 s after standing up. After the initial reduction, blood pressure usually recovers in about 20 s. This recovery can be delayed in the elderly and in patients with neurodegenerative disorders. …