Proceedings of The Physiological Society

University of Oxford (2011) Proc Physiol Soc 23, PC76

Poster Communications

Brain blood flow and cardiovascular responses to hot flashes in symptomatic postmenopausal women.

R. A. Lucas1,2, M. S. Ganio1,2, J. Pearson1,2, C. G. Crandall1,2

1. Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, Texas, United States. 2. Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States.

Hot flashes can significantly reduce blood pressure in some symptomatic women. However, it is unknown whether this drop in blood pressure compromises cerebral perfusion. Objective: This study tested the hypothesis that cerebral perfusion is reduced during the postmenopausal hot flash. Method: Eleven healthy, normotensive, postmenopausal women rested in a temperature-controlled laboratory (~25°C) for approximately 120 minutes while waiting for a hot flash to occur. The onset of a hot flash was objectively identified by an increase in sternal skin blood flow (laser Doppler flowmetry) and/or sternal sweat rate (capacitance hygrometry). Middle cerebral artery blood velocity (MCAvmean, transcranial Doppler), mean arterial blood pressure (MAP, Finometer®), systolic aortic blood velocity (Doppler of ascending aorta, an index of stroke volume) and heart rate (HR, electrocardiogram) were measured continuously. Cerebrovascular resistance (CVR) was calculated as MCAvmean /MAP. Data were averaged into 10 s segments to identify the maximum drop in MAP during the hot flash. For each hot flash, all physiological responses at the period of the maximal drop in MAP were compared to the resting baseline value taken immediately prior to a hot flash. Results: Twenty-seven hot flashes occurred during the experimental sessions (lasting 6.2 ±2.8 min, 3 ±1 hot flashes per participant). The average maximum decrease in MAP during the hot flashes was 12 ±5 mm Hg (P <0.01). At the maximum decrease in MAP, there was a modest reduction in both MCAvmean (4 ±7 cm.s-1, P =0.01) and CVR (0.1 ± 0.3, P =0.01), while systolic aortic blood velocity and HR did not change (P >0.05 for both) Conclusion: A hot flash can be accompanied by a significant acute reduction in MAP in symptomatic postmenopausal women. However, this response corresponded to a small decrease (i.e., 6 ±1%) in cerebral perfusion as measured by MCAvmean. Thus, hot flashes only mildly perturb cerebral perfusion. Supported by NIH Grant AG030189

Where applicable, experiments conform with Society ethical requirements