Woman Gives Surprise Insight Into Hot Flashes

By Amanda Gardner
HealthDay Reporter

FRIDAY, Oct. 8 (HealthDayNews) -- A purely chance combination of events may have provided researchers with new insight into a stubbornly persistent women's health issue: the hot flash.


A hypertensive woman participating in a study about sleep, stress, and blood pressure happened to have a hot flash. Equipment set up to monitor the woman's blood pressure recorded a dramatic decline in that pressure.


"She had the blood pressure device on that allowed us to measure blood pressure, and she spontaneously noted that she was developing a hot flash. This does let us document for the first time the profound change in blood pressure and the heart rate response as an effort to counteract the drop in blood pressure," said Dr. Joel E. Dimsdale, professor of psychiatry at the University of California, San Diego. "We took advantage of serendipitous events. We were studying this woman for other reasons."


"You would expect blood pressure to drop. The thing that was striking to us was the magnitude of the drop," continued Dimsdale, who is co-author of a letter documenting the findings in the Oct. 7 issue of the New England Journal of Medicine (news - web sites). "We were stunned by the magnitude of the response."


Hot flashes are a commonplace event in women entering and well into menopause; according to some estimates, two in three women will experience them. Still, scientists still do not have a clear understanding of the mechanism behind them.


Certainly, hot flashes are associated with fluctuations in heart rate and flushing. "What we haven't known has been the moment-to-moment observations of blood pressure," Dimsdale said.


The reason for this is that only recently has the equipment been available to noninvasively measure blood pressure heartbeat to heartbeat. "If you were to have a hot flash and wanted to know your blood pressure, by the time you could go grab a blood pressure cuff and pump it up, it would all be past," Dimsdale explained.


Serendipity conspired to change that.


The 46-year-old, unidentified woman participating in an unrelated study happened to report a hot flash while hooked up to a device that provided continuous, beat-to-beat blood pressure recording. During the flash, her blood pressure dropped substantially, by 40 millimeters of mercury, followed by a rise in heart rate.


Heartbeat typically accelerates after a drop in blood pressure as a way to compensate. Researchers had speculated that this "baroreflex," which essentially works to stabilize blood pressure, was linked to certain changes that took place during a hot flash.


When researchers asked other women in the study to inhale amyl nitrate, which makes blood vessels wider, a number of menopausal women reported having hot flashes.


The findings raise the question of whether women who have impaired baroreflex functioning, such as women with autonomic neuropathy, might also suffer worse menopausal symptoms. Autonomic neuropathy occurs when the nerves that regulate the part of the nervous system that is not under your conscious control are damaged.


So far, however, the researchers have information on only one woman -- and a woman with high blood pressure at that. There is no way to generalize to other women.


"One would expect that if blood pressure drops, that the heart would compensate. But why does this happen in women going through menopausal treatment?" asked Dr. Steven Goldstein, professor of obstetrics and gynecology at New York University School of Medicine. "There's no clue to that in this report."