NEW YORK • Orthostatic hypotension refers to a brief but precipitous drop in blood pressure that causes light-headedness or dizziness when standing up after lying down or sitting, and sometimes even after standing, for a prolonged period.
The problem is likely to be familiar to people of all ages, but middle-aged and older adults are most frequently affected.
Orthostatic hypotension is also a risk factor for strokes and heart attacks. It can be an early warning sign of a serious underlying cardiovascular or neurological disorder.
Under normal circumstances, when we stand up, gravity temporarily causes blood to pool in the lower half of the body; then, within 20 or 30 seconds, receptors in the heart and carotid arteries in the neck trigger a compensating mechanism called the baroreflex that raises the heart rate and constricts blood vessels to increase blood pressure and provide the brain with an adequate supply of blood.
In people with orthostatic hypotension, this reflex mechanism is delayed or insufficient, resulting in such symptoms as light-headedness, dizziness or fainting.
The disorder is officially defined as a drop in systolic blood pressure (the top number) of 20 or more millimetres of mercury or a drop of 10 or more in diastolic pressure (the bottom number) within three minutes of standing upright.
However, a study of 11,429 middle-aged adults followed for up to 23 years found that blood pressure measurements taken within one minute of standing were even more strongly related to dizziness, falls, fractures, motor vehicle accidents and death than recordings done after three minutes.
"Some patients recover and you may miss the problem when you wait three minutes to measure blood pressure," said Dr Stephen Juraschek, an internist at Beth Israel Deaconess Medical Centre in Boston and assistant professor of medicine at Harvard Medical School, who directed the study.
He said that while orthostatic hypotension is commonly regarded as a neurological problem, "it's associated with a lot of sub-clinical cardiovascular pathology, which is probably the largest contributor".
Dr Lewis Lipsitz, geriatrician and director of the Marcus Institute for Ageing Research in Boston, said people with especially high blood pressure are more susceptible to orthostatic hypotension because hypertension impairs the heart's ability to pump blood, thickens blood vessels that then cannot constrict and impairs kidney function.
"Every patient on medication to lower blood pressure should be checked periodically for orthostatic hypotension during routine office visits," he said.
He suggested that patients lie down for three to five minutes, then have repeated blood pressure checks done, in the first 20 to 30 seconds, after one minute and again after three minutes of standing up.
He explained that when a person stands up, about 500ml of blood pools in the legs and belly. In older people, the increase in heart rate and blood vessel constriction needed to compensate this is less effective.
Recommended treatments include wearing compression stockings and an abdominal binder (a girdle) to reduce the pooling of blood upon standing. Also helpful is avoiding prolonged or motionless standing, as well as hot baths or showers.
NYTIMES
