Hemodynamic characteristics of sodium-sensitive human subjects.

Abstract

SUMMARY Fifty-eight normal subjects and 51 subjects with borderline hypertension underwent microvascular and hemodynamic studies while on an ad libitum diet and during periods of sodium depletion (10 mEq/day) and repletion (200 mEq/day). Hemodynamic measurements included arterial blood pressure, cardiac index, total peripheral resistance, forearm blood flow, vascular resistance, venous compliance, and capillary filtration fraction. Studies of the mlcrocirculation consisted of macrophotography of the buibar conjunctiva with measurement of anteriolar, venular, and capillary density and diameter. During sodium repletion, cardiac index increased significantly in the normal subjects (2.35 ± 0.7 vs 2.44 ± 0.7 L/min/m 2 ; p<0.01) and in the borderline hypertensive subjects (2.50 ± 0.7 vs 2.70 ± 0.8 L/min/m 2 ; p<0.01). However, mean blood pressure rose by more than 5% in only 33 subjects, 13 with normal and 20 with borderline hypertension. When these sodium-sensitive subjects were compared with those whose blood pressure did not rise, the former were found to have significantly higher forearm vascular resistance (32.2 ± 21 vs 17.9 ± 12 mm Hg/ml/min/lOOg; p<0.01), lower forearm blood flow (4.42 ± 2.7 vs 7.47 ± 5.0 ml/min/100 g) and lower conjunctival capillary density (3.72 ± 1.7 vs 5.18 ±2.1 [SD] mm/mm 2 ; p< 0.05). These results indicate that sodium sensitivity In humans is accompanied by elevation of forearm vascular resistance and attenuation of the microcirculatton. (Hypertension 9: 398-406, 1987) KEY WORDS • hypertension microcirculation sodium • vascular resistance * hemodynamics T HE conclusion that certain individuals are sodium-sensitive is supported by two main lines of evidence, experimental and epidemiological. Meneely et al. 1 found that rats fed a high sodium diet displayed a wide spectrum of blood pressure responses: some became severely hypertensive, some remained normotensive, and others manifested intermediate levels of blood pressure elevation. After several generations of selective inbreeding, Dahl et al. were able produce strains of genetically sodium-sensitive and sodium-resistant rats. Received December 16, 1985; accepted December 10, 1986. While studies within populations have not shown a direct relationship between individual sodium intake and blood pressure, possibly because of a saturation effect, studies of human populations have also supported the concept of individual susceptibility to the hypertensive effects of sodium. Several surveys have demonstrated a positive relationship between sodium intake and the prevalence of hypertension.3 However, normotensive persons can be found even in populations ingesting large quantities of sodium, suggesting that some humans are sodium-resistant while others are sodium-sensitive. 4 A number of investigators have observed abnormalities in the vascular resistance of patients with early, mild hypertension that might underlie sodium sensitivity. "12 The purpose of the present study was to identify persons whose blood pressure rises with increases in ...

Effect of chronic sodium loading on cardiovascular response in young blacks and whites.

“…Using the criteria reported by Sullivan et al, 25 subjects with a 5% increase in MAP from levels before sodium loading were considered sodium sensitive. Subjects with less than 5% increase in MAP were classified as sodium insensitive.…”

“…In a young adult population, Sullivan et al 25 reported an association of sodium sensitivity with elevation of forearm vascular resistance in both normotensive and borderline hypertensive individuals.…”

“…The rigorous vascular hemodynamic studies at differing levels of sodium intake that were performed by Sullivan et al 25 have not been performed on a young black population, but will be of value in light of emerging evidence on racial differences in hypertension.…”

Dietary sodium effects on heart rate variability in salt sensitivity of blood pressure

“…Medical personnel performed a physical examination, a comprehensive medical history, electrocardiogram (EKG) and obtained blood and urine samples to ensure that the participants met the study entry criteria. Each qualifying subject participated in a 12-day experiment consisting of six days on a low sodium diet followed immediately by six days on a high sodium diet, similar to those in previous studies laboratories (Sullivan, Prewitt, Ratts, Josephs, & Connor 1988;Anderson et al, 1998;Coruzzi, et al, 2005). Participants were given low sodium-low potassium meals in insulated containers, and provided with dietary logs to record food intake to augment adherence to the diet.…”

Normal Exercise Blood Pressure Response in African-American Women with Parental History of Hypertension

“…The number of subjects included in the present study was based on data indicating that the critical detectable differences in total peripheral resistance (TPR) measured at rest for differentiating between groups of normotensive versus hypertensive subjects was 23%, 19 of normotensive versus borderline hypertensive subjects was 32%, 20 and of normal and borderline hypertensive salt-sensitive versus salt-insensitive subjects was 44%. 21 The parents of the participants were identified as normotensive (systolic pressure <140 mm Hg and diastolic pressure <90 mm Hg) or hypertensive (systolic pressure >140 mm Hg or diastolic pressure >90 mm Hg) by personal telephone calls, or on the basis of replies to a questionnaire given to participants to assess their parents' medical blood pressure histories. Most of the parents with hypertension had stage II (moderate) hypertension and all were receiving pharmacological treatments, with some parents receiving pharmacological and nonpharmacological treatments for the condition.…”