Hot-Flash Hypotension
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《新英格兰医药杂志》
To the Editor: The hot flash is one of the most commonly encountered symptoms of menopause, yet there is little understanding of its underlying physiology. With its unpredictable onset and evanescent nature, this troubling symptom has been difficult to study. The peripheral vasodilatation and rise in skin temperature are readily apparent, but what else happens during a hot flash?
A 46-year-old, hypertensive, black woman was participating in a study in which we were examining the relationship of sleep and stress to hypertension. On enrolling in the study, she reported having menopausal symptoms, including hot flashes.
A continuous beat-to-beat blood-pressure recording (Colin Pilot, Colin Medical Instruments) was obtained as part of the larger study protocol, and the observations during a hot flash were strictly serendipitous. The patient reported experiencing a hot flash during a resting baseline period of the testing. Simultaneously, the technician observed that the patient was sweating profusely and that her blood pressure had dropped by more than 40 mm Hg. Figure 1 shows the 3-minute recording of the patient's heart rate and systolic blood pressure, smoothed to 10-second intervals, around the time of the hot flash and during the second resting interval, without a hot flash, approximately 30 minutes later. Figure 2 shows the mean (±SE) resting systolic blood pressure and heart rate in four other black women with blood pressure levels, body-mass index, and age that were similar to those of the first woman, who were tested under the same protocol. None of these women reported hot flashes during testing.
Figure 1. Blood Pressure and Heart Rate Measured during a Hot Flash.
Black circles show blood pressure and heart rate during a hot flash. White circles show the values during a second baseline measurement 30 minutes later.
Figure 2. Blood Pressure and Heart Rate in Four Women without Hot Flashes.
The women were matched for blood-pressure level, age, and body-mass index with the woman who had the hot flash. I bars denote standard errors.
As Figure 1 shows, there was a substantial decrease in blood pressure during the hot flash. This decrease was quickly followed by a rise in the heart rate. The acute drop in blood pressure accompanied by the equally brisk increase in the heart rate is typical of the baroreflex response to an acute hypotensive episode. It has been speculated, but not documented, that the thermogenic changes occurring during a menopausal hot flash are baroreflex-related.1,2 When we tested baroreflex tone by having the participants inhale the vasodilator amyl nitrite, a number of menopausal women spontaneously reported that they felt as though the medication was giving them a hot flash. These observations add new depth to our understanding of "vasomotor instability," long reported to be a hallmark of menopausal symptoms. Given the corrective role of the baroreflex response in this setting, one wonders whether menopausal symptoms are more severe in women whose baroreflex functioning is impaired (e.g., women with autonomic neuropathy).
Richard Nelesen, Ph.D.
Pattie Krohn, B.A.
Joel E. Dimsdale, M.D.
University of California, San Diego
La Jolla, CA 92093
jdimsdale@ucsd.edu
References
Charkoudian N. Skin blood flow in adult human thermoregulation: how it works, when it does not, and why. Mayo Clin Proc 2003;78:603-612.
Freedman RR. Biochemical, metabolic, and vascular mechanisms in menopausal hot flashes. Fertil Steril 1998;70:332-337.
A 46-year-old, hypertensive, black woman was participating in a study in which we were examining the relationship of sleep and stress to hypertension. On enrolling in the study, she reported having menopausal symptoms, including hot flashes.
A continuous beat-to-beat blood-pressure recording (Colin Pilot, Colin Medical Instruments) was obtained as part of the larger study protocol, and the observations during a hot flash were strictly serendipitous. The patient reported experiencing a hot flash during a resting baseline period of the testing. Simultaneously, the technician observed that the patient was sweating profusely and that her blood pressure had dropped by more than 40 mm Hg. Figure 1 shows the 3-minute recording of the patient's heart rate and systolic blood pressure, smoothed to 10-second intervals, around the time of the hot flash and during the second resting interval, without a hot flash, approximately 30 minutes later. Figure 2 shows the mean (±SE) resting systolic blood pressure and heart rate in four other black women with blood pressure levels, body-mass index, and age that were similar to those of the first woman, who were tested under the same protocol. None of these women reported hot flashes during testing.
Figure 1. Blood Pressure and Heart Rate Measured during a Hot Flash.
Black circles show blood pressure and heart rate during a hot flash. White circles show the values during a second baseline measurement 30 minutes later.
Figure 2. Blood Pressure and Heart Rate in Four Women without Hot Flashes.
The women were matched for blood-pressure level, age, and body-mass index with the woman who had the hot flash. I bars denote standard errors.
As Figure 1 shows, there was a substantial decrease in blood pressure during the hot flash. This decrease was quickly followed by a rise in the heart rate. The acute drop in blood pressure accompanied by the equally brisk increase in the heart rate is typical of the baroreflex response to an acute hypotensive episode. It has been speculated, but not documented, that the thermogenic changes occurring during a menopausal hot flash are baroreflex-related.1,2 When we tested baroreflex tone by having the participants inhale the vasodilator amyl nitrite, a number of menopausal women spontaneously reported that they felt as though the medication was giving them a hot flash. These observations add new depth to our understanding of "vasomotor instability," long reported to be a hallmark of menopausal symptoms. Given the corrective role of the baroreflex response in this setting, one wonders whether menopausal symptoms are more severe in women whose baroreflex functioning is impaired (e.g., women with autonomic neuropathy).
Richard Nelesen, Ph.D.
Pattie Krohn, B.A.
Joel E. Dimsdale, M.D.
University of California, San Diego
La Jolla, CA 92093
jdimsdale@ucsd.edu
References
Charkoudian N. Skin blood flow in adult human thermoregulation: how it works, when it does not, and why. Mayo Clin Proc 2003;78:603-612.
Freedman RR. Biochemical, metabolic, and vascular mechanisms in menopausal hot flashes. Fertil Steril 1998;70:332-337.