National Organization for Rare Disorders, Inc.
It is possible that the main title of the report Hypotension, Orthostatic 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 and the blood pools 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.
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, 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.
Some clinical neurologists prefer to focus on three primary syndromes of the failure or breakdown of the autonomic nervous system. These are:
Acute or subacute idiopathic pandysautonomia (ASIP) refers to the breakdown of the autonomic nervous system (control of breathing, blood circulation, pain, taste, etc.) from unknown causes.
Pure autonomic failure (PAF) is sometimes defined as the presence of orthostatic hypotension (without an identifiable cause such as medically prescribed drugs) without evidence of any other neurological problem(s). This term, according to an international consensus committee, replaces Bradbury-Egglestone syndrome, idiopathic orthostatic hypotension, and progressive autonomic failure.
National Institute of Neurological Disorders and Stroke (NINDS)
P.O. Box 5801
Bethesda, MD 20824
Autonomic Dysfunction Center
Vanderbilt University Medical Center
Nashville, TN 37232-2195
National Dysautonomia Research Foundation
PO Box 301
Red Wing, MN 55066-0102
Genetic and Rare Diseases (GARD) Information Center
PO Box 8126
Gaithersburg, MD 20898-8126
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