It is possible that the main title of the report Orthostatic Hypotension is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.
Orthostatic hypotension (OH) describes an extreme drop in blood pressure that may occur when a person stands up suddenly causing the blood to pool in the blood vessels of the legs. Because of this pooling, the amount of blood carried back to the heart by the veins is decreased. Subsequently, less blood is pumped out from the heart, resulting in a sudden drop in blood pressure. By definition, the drop in blood pressure must be greater than 20 mm of mercury during contraction of the heart muscles (systole) and more than 10 mm of mercury during expansion of the heart muscles (diastole). Among children and teenagers, short-lived episodes of OH are normal and not uncommon. Episodes among the elderly are always to be taken seriously. Furthermore, feeling light-headed when first standing up is not cause for alarm, but losing consciousness, even if only briefly, should be reported to a medical professional immediately.
Normally, specialized cells in the body (baroreceptors) quickly respond to changes in blood pressure. These baroreceptors then activate the autonomic nervous system to increase, via reflex action, and increase levels of catecholamines (e.g. epinephrine, norepinephrine) in the body. Increased catecholamine levels rapidly restore the blood pressure. A defect in this spontaneous response (reflex) prevents the heart rate and blood pressure from rising adequately and orthostatic hypotension results. Fainting and falling are the usual consequences.
NIH/National Institute of Neurological Disorders and Stroke
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Vanderbilt's Autonomic Dysfunction Center
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