Orthostatic hypotension is a condition in which blood pressure drops abnormally when a person stands up. The drop in blood pressure can lead to weakness, lightheadedness, dizziness or syncope (temporary loss of consciousness, lasting from seconds to a few minutes).
Orthostatic hypotension can occur in anybody, but it is far more common in older people. In fact, orthostatic hypotension is perhaps the most common cause of falls, broken bones and head injuries among the elderly.
What Causes Orthostatic Hypotension?Normally, when we stand up the blood vessels in our legs constrict to prevent blood from pooling in our legs. This vascular constriction improves the return of blood to our hearts and supports our blood pressure when we are upright.
In older people, this normal blood vessel constriction tends to occur less efficiently. Up to 20% of people over 65 will have an exaggerated drop in blood pressure when standing. In the majority of these people the drop is not severe enough to produce symptoms. But if they also have diabetes, drink alcohol or take one of several medications (including nitrates, antidepressants, opiates, oral hypoglycemic drugs or medications for hypertension) the drop in blood pressure may become pronounced enough to cause symptoms.
Orthostatic hypotension can also be seen in younger people, though much less frequently than in the elderly. When it is seen in young or middle-aged individuals, it tends to be caused by dehydration, prolonged bedrest (that is, deconditioning), excessive bleeding or dysautonomia.
Vasovagal syncope - or a "simple" fainting spell - is a particular form of orthostatic hypotension. It is caused by a transient reflex that produces sudden dilation of the blood vessels in the legs, causing blood to pool in the lower extremities and producing loss of consciousness when upright.
Postprandial hypotension is a type of orthostatic hypotension that occurs after meals. Postprandial hypotension is caused by blood pooling in the abdominal organs during digestion.
There are also several neurological conditions, such as diabetic neuropathy and multiple system atrophy, that produce orthostatic hypotension. Most often these conditions are accompanied by other fairly obvious signs of a neurological disorder.
Orthostatic hypotension is not the same thing as postural orthostatic tachycardia syndrome (POTS), a disorder of younger people (generally, in people under 45 years old) in which an increase in heart rate while standing (rather than a decrease in blood pressure) is the cause of symptoms.
How Is Orthostatic Hypotension Diagnosed?Doctors should become suspicious of orthostatic hypotension whenever an older patient complains of episodes of lightheadedness or general weakness. Indeed, because orthostatic hypotension is so common in the elderly and so often leads to broken bones or worse, doctors should take care to check for it whenever older people describe almost any kind of "episode." This is especially true if they are taking medications that can cause this condition.
Orthostatic hypotension is diagnosed simply by measuring a drop in blood pressure when standing. The doctor should first take the blood pressure after the patient has been lying for several minutes, and then repeat the measurement after the patient has been standing upright for two to five minutes.
Orthostatic hypotension is diagnosed if there is a greater than 20 mmHg fall in systolic blood pressure (the upper number in the blood pressure reading), or a greater than 10 mmHg fall in diastolic blood pressure (the lower number in the blood pressure reading). It can also be diagnosed if the patient has symptoms of lightheadedness or dizziness after standing and that are accompanied by any drop in systolic or diastolic blood pressures.
In people with orthostatic hypotension, the heart rate usually also increases by 10 beats per minute or more while standing. But (in contrast to POTS), the drop in blood pressure is the predominant finding.
How Is Orthostatic Hypotension Treated?If you have orthostatic hypotension, the key to treatment is to identify the reason for the drop in blood pressure. Once the cause is known, the orthostatic hypotension can usually be treated effectively.
Do you have dehydration from vomiting or lack of appetite, bleeding or from taking diuretic pills? Are you in poor condition due to a recent illness? Are you taking blood pressure medications, antidepressants or nitrates? Do you drink alcohol? All of these causes of orthostatic hypotension are reversible.
A common dilemma in elderly people is how to treat their elevated blood pressure without producing orthostatic hypotension. In some cases, the best solution is to use blood pressure medication only to the extent that orthostatic hypotension can be avoided. That is, the blood pressure should not be "pushed" down to levels where orthostatic hypotension occurs.
If there is no readily reversible cause for orthostatic hypotension, other treatment measures must be used. These measures may include expanding the blood volume (by increasing salt and water intake, or with the prescription drug fludrocortisone); an exercise program to improve vascular conditioning; using custom-fitted elastic stockings; actively tensing the leg muscles when standing upright (which improves blood return to the heart); or taking midodrine (Mestinon), a medication that increases vascular tone and helps prevent blood pooling.
SummaryOrthostatic hypotension is a common cause of injury, particularly among the elderly. Doctors should always be alert to this condition, especially since it is usually so readily treatable.
Rutan GH, Hermanson B, Bild DE, et al. Orthostatic hypotension in older adults. The Cardiovascular Health Study. CHS Collaborative Research Group. Hypertension 1992; 19:508.
Shibao C, Grijalva CG, Raj SR, et al. Orthostatic hypotension-related hospitalizations in the United States. Am J Med 2007; 120:975.