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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.
The common symptoms of OH include a precipitous drop in blood pressure on rising from a reclining position, changes in patterns of sweating, changes in digestion, impotence, bladder malfunction, and fatigue. Other symptoms reported include dizziness, blackouts, nausea, fuzzy vision, headaches.
While the milder symptoms of OH may be more of a nuisance than a serious concern, more serious complications are possible. These complications include stroke and some types of brain damage.
Orthostatic hypotension may be a temporary condition or one that occurs consistently over time (chronic). It may present as a sole symptom that occurs for no apparent reason (idiopathic) or due to the use of a certain medications, or it may occur as a secondary condition resulting from an underlying, primary disorder.
A common cause of orthostatic hypotension is the decrease in volume of circulating blood (hypovolemia) resulting from excessive use of medications that increase urination (diuretics), or from drug therapy (i.e., calcium blockers and nitrates) for the treatment of high blood pressure, heart failure or chest pains (angina pectoris). A variety of drugs that interfere with the autonomic nervous system's reflexes can also cause OH, such as certain antipsychotic (i.e., phenothiazine) and antidepressant drugs. Additional drugs have been reported to cause OH, including alcohol, barbiturates, and the chemotherapeutic drug vincristine.
OH may be associated with Addison's disease, atherosclerosis (hardening of the arteries as a consequence of the accumulation of fatty deposits), diabetes and some of the neurological disorders that affect the autonomic nervous system, such as multiple system atrophy and Shy-Drager syndrome. OH may accompany disorders that affect muscles and nerves, hence movement, without obvious external or internal stimuli. Progressive diseases of the spinal cord such as syringomyelia may also be associated with OH.
Neurologic disorders that involve the autonomic nervous system may interrupt or damage the automatic reflexes that occur upon standing. Orthostatic hypotension may result from neurological damage due to syphilis, diabetic neuropathy, or numerous other neurological disorders.
OH is most common in the elderly, postpartum mothers, those who have been on bed rest, and teenagers, because of their large amounts of growth over a small time period. Eating disorders such as anorexia nervosa and bulimia nervosa have been known to trigger OH. Large amounts of alcohol consumption can dehydrate the body significantly and thus may lead to OH.
Symptoms of the following disorders can be similar to those of orthostatic hypotension. Comparisons may be useful for a differential diagnosis:
Shy-Drager syndrome is a rare neurological disorder characterized by progressive failure of the autonomic nervous system, the part of the nervous system that controls a variety of vital involuntary bodily functions. These include regulation of heart rate, blood pressure, sweating, bowel and bladder control, as well as a variety of other bodily functions. Symptoms of Shy- Drager syndrome include unusually low blood pressure while standing upright, loss of bladder and bowel control, and/or lack of sweating. (For more information on this disorder, choose "Shy-Drager" as your search term in the Rare Disease Database.)
Vasovagal syncope is a disorder in which there is a temporary impairment of blood circulation in the brain. It may occur during emotional stress, pain or mild shock. It may also result from prolonged bed rest, anemia, fever, fasting or mild heart disease. Symptoms include low blood pressure (orthostatic hypotension), a brief loss of consciousness (fainting), and pale and cold extremities (fingers and toes). Attacks may last from a few minutes to hours, and occurrence is at irregular intervals.
Although the symptoms are sometimes vague, OH can be diagnosed by a simple test of an individual's blood pressure when sitting down and then immediately standing up. A significant fall in blood pressure during this test will indicate OH. Heart rate is also monitored in both the sitting and standing position and can aide in diagnosis. A tilt table test may also be conducted in order to assess blood pressure. In this test, a patient will lie flat on a special table or bed while connected to an ECG and blood pressure monitors. The table then tilts to create a change in posture from lying to standing.
Treatment of orthostatic hypotension depends upon the cause. When caused by a decrease in volume of circulating blood (hypovolemia) due to the use of certain medication(s), it is easily treated by adjusting the dosage or discontinuing the medication, under a doctor's supervision. Low blood pressure resulting from extended bed rest can be corrected by allowing the affected individual to sit up each day at certain times with increasing frequency. The drug ephedrine may be administered orally, and in some cases salt intake may be increased. Maintaining an elevated salt-intake may be prescribed, either through sodium supplements or drinks containing electrolytes. Drinking a large quantity of fluids also can aide in preventing OH episodes by preventing dehydration.
In some cases, the legs may be fitted for elastic stocking that can help maintain blood pressure upon standing. Inflatable antigravity suits may be used in more severe cases to create enough pressure on the legs and abdominal area to raise blood pressure.
Some relief may be afforded by taking some simple precautions such as avoiding hot baths that lower blood pressure, changing diet to avoid constipation and to help control blood pressure, and taking medications that help raise blood pressure, strengthen bladder tone, or prevent constipation.
The drug midodrine hydrochloride (Amatine, ProAmatine, Gutron) has been approved by the FDA to treat OH by reducing the radius of blood vessels and thus, increasing blood pressure.
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FROM THE INTERNET
Tam Sing, J. Idiopathic Orthostatic Hypotension and other Autonomic Failure Syndromes.Medscape Reference. Last Updated: 11/18/09. http://emedicine.medscape.com/article/1154266-overview
NINDS Orthostatic Hypotension Information Page. 2/14/07.
Report last updated: 2011/09/15 00:00:00 GMT+0