Heart rate increases linearly in response to acute XXXX .

@entity1 @entity1168 @entity417 @entity235
BACKGROUND: The cardiovascular response to acute @entity417 in @entity1 is thought to differ from that of other species. Studies of anesthetized @entity1 have found either no change or a @entity1168 . A previous study showed that in 32 healthy unmedicated @entity1 , heart rate increased during acute @entity417 . The hypothesis that heart rate in @entity1 increases in response to acute @entity417 and that the increase is affected by gender was tested. STUDY DESIGN AND METHODS: Acute @entity417 to a Hb concentration of approximately 5 g per dL in 95 unmedicated healthy @entity1 was produced by simultaneous withdrawal of blood and IV replacement with 5-percent HSA and autologous platelet-rich plasma. The relationship between heart rate and Hb concentration was examined using a mixed-effects linear regression model that allowed each @entity1 to have a fitted line with its own slope and intercept. Cubic and quadratic terms were added to determine if these improved the goodness of fit. The effect of gender was tested by including it and its interactions with Hb in the mixed model. RESULTS: The relationship between heart rate and Hb concentration was linear (p < 0.001) and consistent among the population studied: heart rate = 116.0-4.0 [Hb] (slope 95% CI: -4.2 to -3.8 beats/min/g Hb). Adding a cubic or quadratic term did not significantly improve the goodness of fit of the mathematical expression to the data, confirming the linear nature of the relationship between heart rate and Hb concentration. For @entity1 , the slope of the heart rate response was significantly greater than it was for males (difference +/- SE: 0.70 +/- 0.23, p < 0.005). CONCLUSION: In 95 unmedicated, healthy @entity1 , heart rate was a linear function of Hb during acute @entity417 . Females had a significantly greater slope of increase in heart rate with decreasing Hb concentration than did males. The relationship is consistent among individuals, is similar to that reported for conscious @entity235 , and differs from that found previously in anesthetized @entity1 .
