Central hemodynamic responses to an acute sodium load
Date
2005
Authors
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Publisher
University of Delaware
Abstract
Chronically high dietary sodium intake has been associated with elevated blood pressure. Many studies have shown that black adults demonstrate a higher degree of sodium sensitivity and vascular reactivity than white adults. PURPOSE: To examine the acute effects of sodium on blood pressure, cardiac output, and peripheral vascular resistance in black and white subjects. We hypothesized that the hypertonic saline infusion would elicit an increase in blood pressure that would be more robust in black subjects. METHODS: 11 healthy black and 15 healthy white subjects underwent a hypertonic saline (3%) infusion lasting 60 minutes. Blood pressure and cardiac output were assessed at baseline, 20, 40, and 60 minutes into the infusion. Blood was drawn for the analysis of serum sodium, osmolality, hematocrit, at baseline, 15, 30, 45, and 60 minutes into the infusion. Plasma volume and peripheral vascular resistance were calculated. Results are reported as means ± standard errors and a two way ANOVA was used to compare the effects of time and race. RESULTS: During the infusion, serum sodium (135.9 ± 0.4 to 141.7 ± 0.5 mmol/L), osmolality (288.8 ± 0.6 to 297.8 ± 0.7), plasma volume (18.0 ± 1.9%), mean arterial blood pressure (80.7 ± 2.3 to 91.9 ± 2.6 mmHg) and cardiac output (4.3 ± 0.2 to 4.8 ± 0.3 L/min) significantly increased in both groups (p < 0.05). There was a time effect for peripheral vascular resistance. White subjects demonstrated a greater increase in plasma volume compared to black subjects (21.46 v 13.78, p=0.03). CONCLUSION: The hypertonic saline infusion caused a significant increase in blood pressure that was not different between black and white subjects.