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Blood pressure and hemodynamic responses to an acute sodium load in humans

Departments of ¹Health, Nutrition, and Exercise Sciences, and ²Nursing, University of Delaware, Newark; and ³Christiana Care Health Services, Cardiovascular Research, Newark, Delaware

Submitted 7 March 2005 ; accepted in final form 20 June 2005

The purpose of this study was to investigate the acute blood pressure (BP) and hemodynamic effects of sodium chloride (3% intravenous solution). Although many studies link a change in dietary sodium to a change in BP, few consider the effects of sodium concentration in the blood on BP. We hypothesized that an intravenous sodium load would increase BP, and we quantified alterations in cardiac output (c) and peripheral vascular resistance (PVR). Thirteen subjects (age 27 ± 2 yr) underwent a 60-min 3% saline infusion (0.15 ml·kg^–1·min^–1). BP was assessed on a beat-to-beat basis with a Finometer, c was assessed via the CO₂ rebreathing technique, and PVR was derived. Serum sodium and osmolality increased, and hematocrit declined during the infusion (ANOVA, P < 0.01). Mean arterial pressure (MAP) increased continuously during the infusion from 81.8 ± 3.4 to 91.6 ± 3.6 mmHg (ANOVA, P < 0.01). BP responsiveness to sodium was expressed as the slope of the serum sodium-MAP relationship and averaged 1.75 ± 0.34 mmHg·mmol^–1·l^–1. BP responsiveness to the volume change was expressed as the slope of the hematocrit-MAP relationship and averaged –2.2 ± 0.35 mmHg/%. The early change in MAP was mediated by an increase in c and the late change by an increase in PVR (P < 0.05), corresponding to a 30% increase in plasma norepinephrine. In conclusion, an acute infusion of hypertonic saline was effective in increasing BP, and both sodium and volume appear to be involved in this increase; acute BP responsiveness to serum sodium can be quantified using a MAP-sodium plot.

cardiac output; peripheral vascular resistance; salt sensitivity; hypertension

This article has been cited by other articles:

				W. B. Farquhar, M. M. Wenner, E. P. Delaney, A. V. Prettyman, and M. E. Stillabower Sympathetic neural responses to increased osmolality in humans Am J Physiol Heart Circ Physiol, November 1, 2006; 291(5): H2181 - H2186. [Abstract] [Full Text] [PDF]