Low blood pressure on standing up (postural or orthostatic hypotension)
This is a sudden drop in blood pressure when you stand up from a sitting position or if you stand up after lying down. Ordinarily, gravity causes blood to pool in your legs whenever you stand. Your body compensates for this by increasing your heart rate and constricting blood vessels, thereby ensuring that enough blood returns to your brain. But in people with postural hypotension, this compensating mechanism fails and blood pressure falls, leading to symptoms of dizziness, lightheadedness, blurred vision and even fainting.
Postural hypotension can occur for a variety of reasons, including dehydration, prolonged bed rest, pregnancy, diabetes, heart problems, burns, excessive heat, large varicose veins and certain neurological disorders. A number of medications can also cause postural hypotension, particularly drugs used to treat high blood pressure — diuretics, beta blockers, calcium channel blockers and angiotensin-converting enzyme (ACE) inhibitors — as well as antidepressants and drugs used to treat Parkinson’s disease and erectile dysfunction.
Postural hypotension is especially common in older adults, with as many as 20 percent of those over age 65 experiencing postural hypotension. But postural hypotension can also affect young, otherwise healthy people who stand up suddenly after sitting with their legs crossed for long periods or after working for a time in a squatting position. Postural hypotension is generally harmless in young people.
[Courtesy of MayoClinic.com]