Hypotension, Orthostatic

Synonyms

• Postural Hypotension

Disorder Subdivisions

• None

General Discussion

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.

Resources

National Institute of Neurological Disorders and Stroke (NINDS)

31 Center Drive

8A07

Bethesda, MD 20892-2540

Tel: (301)496-5751

Fax: (301)402-2186

Tel: (800)352-9424

Email: braininfo@ninds.nih.gov

Internet: http://www.ninds.nih.gov/



Autonomic Dysfunction Center

Vanderbilt University Medical Center

AA3228 MCN

Nashville, TN 37232-2195

USA

Tel: (615)343-6499

Fax: (615)343-8649

Email: david.robertson@vanderbilt.edu

Internet: http://www.mc.vanderbilt.edu/gcrc/adc



National Dysautonomia Research Foundation

PO Box 301

Red Wing, MN 55066-0102

Tel: (651)267-0525

Fax: (651)267-0524

Email: ndrf@ndrf.org

Internet: http://www.ndrf.org

For a Complete Report

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Last Updated:  3/14/2008

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