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Postural (orthostatic) hypotension is defined as a fall in blood pressure of over 20 mm Hg systolic, (or 10 mm Hg diastolic), on standing or during head-up tilt to at least 60°.1 In neurological practice, it may result from diseases or drugs that impair the activity of sympathetic vasoconstrictor nerves. Postural hypotension may be a presenting feature in certain autonomic disorders (such as pure autonomic failure), it may be a pointer towards an alternative diagnosis (as in multiple system atrophy presenting with parkinsonian features), and it may complicate drug therapy (as with levodopa). Postural hypotension is associated with increased morbidity and also mortality, especially in elderly people, in whom falls result in injuries. Advances have resulted in a better understanding of the pathophysiological processes, and in the treatment of postural hypotension.
Recognition and evaluation
Postural hypotension usually is considered when there are characteristic features resulting from cerebral ischaemia such as loss of consciousness (fainting, syncope). Other symptoms may occur (table1).2 Measuring blood pressure while lying and after 2 minutes of standing often confirms a postural fall. However, the lack of a fall, in the presence of suggestive symptoms, should warrant further investigation. There are various disorders, including the chronic fatigue syndrome and the postural tachycardia syndrome, in which postural intolerance may not be accompanied by hypotension. Additional factors may be needed to unmask postural hypotension (table2), especially in mild to moderate autonomic failure.
Further evaluation is best undertaken in an autonomic laboratory. Studies ideally should utilise a tilt table, as patients with neurological disabilities or a profound fall in blood pressure can rapidly and safely be returned to the horizontal position. Additional screening tests (the Valsalva manoeuvre, pressor …
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