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Hypotension

Definition:

Low blood pressure, or hypotension, occurs when blood pressure during and after each heart beat is much lower than usual. This means the heart, brain, and other parts of the body do not get enough blood. Dizziness or lightheadedness can result.

Alternative Names:

Low blood pressure; Blood pressure - low; Postprandial hypotension; Orthostatic hypotension; Neurally mediated hypotension; NMH

Causes, incidence, and risk factors:

Blood pressure that is borderline low for one person may be normal for another. The most important factor is how the blood pressure changes from the normal condition.

Most normal blood pressures fall in the range of 90/60 millimeters of mercury (mm Hg) to 130/80 mm Hg. But a significant drop, even as little as 20 mm Hg, can cause problems for some people.

There are three main types of hypotension:

Orthostatic hypotension, including postprandial orthostatic hypotension
Neurally mediated hypotension (NMH)
Severe hypotension brought on by a sudden loss of blood ( shock )

Orthostatic hypotension is brought on by a sudden change in body position, usually when shifting from lying down to standing. This type of hypotension usually lasts only a few seconds or minutes. If this type of hypotension occurs after eating, it is called postprandial orthostatic hypotension. This form most commonly affects older adults, those with high blood pressure, and persons with Parkinson's disease .

NMH most often affects young adults and children. It occurs when a person has been standing for a long time. You might feel dizzy, faint, or have an upset stomach. Children usually outgrow this type of hypotension.

Severe hypotension starves your body of oxygen, which can cause damage to the heart, brain, and other organs. This type of hypotension can be life threatening if not immediately treated.

Low blood pressure is commonly caused by drugs such as:

Medications used for surgery
Anti-anxiety medications
Heart medicines, including those used to treat high blood pressure and coronary heart disease
Diuretics
Certain antidepressants
Pain killers
Alcohol

Other causes of low blood pressure include:

Dehydration
Heart failure
Heart attack
Changes in heart rhythm ( arrhythmias )
Fainting
Anaphylaxis (a life-threatening allergic response)
Shock (from severe infection, stroke, anaphylaxis, major trauma, or heart attack)
Advanced diabetes

References:

Zipes DP, Libby P, Bonow RO, Braunwald E, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine , 7th ed. St. Louis, Mo; WB Saunders; 2005.

Review Date: 1/19/2007
Reviewed By: Larry A. Weinrauch, MD, Assistant Professor of Medicine, Harvard Medical School, and Private practice specializing in Cardiovascular Disease, Watertown, MA. Review provided by VeriMed Healthcare Network.

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