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There are different kinds of hypotension and the following is one way of classifying them:- Constant Hypotension. The blood pressure is always low, less than 90/60mm Hg. When the blood pressure is too low there is inadequate blood flow to the heart, brain and other vital organs. Borderline low blood pressure for one person may be normal for another. Many people have a chronic problem with low blood pressure that is not particularly serious.
- Temporary Hypotension. The most important factor is how the blood pressure changes from the baseline or normal condition. A fall of 30mm Hg or more from a person’s baseline is considered low blood pressure. This can be caused by any of the following:
- Shock
- Stress/trauma
- Sudden change in posture (orthostatic hypotension)
- Allergy
- Dehydration
- Drug-induced, including alcohol toxicity, anesthesia, antianxiety agents, antihypertensives, calcium channel blockers, diuretics, general anesthetics, antiarrhythmics, monoamine oxidase inhibitors, narcotic analgesics, tranquilizers, vasodilators
- Neurally Mediated Hypotension (NMH). The usual blood pressure may be low, normal or even high, but under certain circumstances blood pressure drops and symptoms develop.
- Age-related decline in blood pressure regulation.
- Secondary to diseases such as central nervous system disorders, for example Shy-Drager syndrome; peripheral neuropathy and autonomic neuropathy (nerve problems), such as may be caused by diabetes mellitus; cardiovascular disorders; nutritional diseases amyloidosis; vitamin deficiencies; spinal cord injuries; Adrenal failure (Addisonian crisis); and neuropathies associated with cancer, particularly lung cancer or pancreatic cancer.
Postural hypotension can happen to anyone for a variety of physiologic reasons, such as dehydration, lack of food, prolonged standing in the heat or being generally run down. Prolonged standing or a tilt test may be needed to detect a delayed hypotensive response. There is a spontaneous improvement in many individuals, although treatment of the cause helps the return to normal.
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