Autonomic neuroscience : basic & clinical
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Clinical Trial
Bell-shaped relationship between central blood volume and spontaneous baroreflex function.
Spontaneous baroreflex function can be altered by acute changes in central blood volume. Both a reduction in spontaneous baroreflex function at central hypovolemia and augmentation at hypervolemia suggest a dose-effect relationship between central blood volume and spontaneous baroreflex function. However, this relationship has not been quantified over stepwise widespread changes in central blood volume. ⋯ Both spontaneous baroreflex indices of high-frequency transfer function gain (LBNP30, 17.4+/-3.2; LBNP15, 22.3+/-3.8; baseline, 25.6+/-4.1; NS15, 28.5+/-4.2 ms mm Hg(-1), ANOVA P=0.001) and of the sequence slope (LBNP30, 14.4+/-2.2; LBNP15, 17.2+/-2.5; baseline, 20.5+/-2.8; NS15, 24.5+/-3.1 ms mm Hg(-1), ANOVA P=0.001) increased stepwise from hypovolemia of LBNP30 to hypervolemia of NS15. However, these indices were lower at NS30 (high-frequency transfer function gain, 22.0+/-2.2 ms mm Hg(-1), post-hoc P=0.071; sequence slope, 17.7+/-1.7 ms mm Hg(-1), post-hoc P<0.05) than NS15 during hypervolemia. These results indicated that the relationship between central blood volume and spontaneous baroreflex function is apparently bell-shaped, with maximal augmentation at moderate hypervolemia.