2017 Volume 38 Pages 67-74
Sudden death in the bath frequently occurs in Japan. It might be partly due to post- bathing orthostatic intolerance and syncope. However, underpinning mechanisms are fully unknown. The aim of this study was to determine the effect of short-term bathing on postural change-related hypotension.
Thirteen healthy men (29-57 yrs) underwent 5-min bathing (41℃) and were measured arterial stiffness (via brachia-ankle pulse wave velocity [baPWV]) and baroreflex sensitivity (BRS) before and after the bathing. BRS was evaluated with the sequence method from mean arterial pressure and heart rate responses to the postural change following the 5-minute sitting in the bath without (control condition) and with hot water (bathing condition).
There was no significant difference in standing-induced hypotension between the control and bathing conditions because of large variability (-32.5±11.2 and -34.2±13.8 mmHg, respectively). Following the bathing baPWV was significantly decreased, whereas BRS gain was significantly attenuated. Extent of standing-induced hypotension was significantly associated with BRS gain (r=-0.736, P=0.006) in the control condition, and then such significant correlation was disappeared after the bathing. Change in orthostatic hypotension (from the control condition to the bathing condition) tended to correlate with BRS gain in the control condition (r=0.531, P=0.076), whereas baPWV did not contribute to change in orthostatic hypotension.
Our results suggest that after the short-term bathing BRS was attenuated but extent of standing-induced hypotension was not influenced remarkably. However, lower BRS might contribute to greater hypotnesion at the orthostatic challenge after the bathing.