Short-term analysis of the relationship between blood pressure and urinary sodium excretion in normotensive subjects

Abstract

The aim of this study was to investigate whether, in the short term, physiological blood pressure changes are coupled with changes in urinary sodium excretion in normotensive subjects, maintained at fixed sodium intake and under controlled postural and behavioural conditions. Twelve normotensive subjects were recruited. For each subject, seven urine samples were collected at fixed time intervals during an overall 26 h period: late afternoon (16.00-20.00 hours), evening (20.00-24.00 hours), night (24.00-06.00 hours), quiet wakefulness (06.00-09.00 hours), morning (09.00-12.00 hours), post-prandial (12.00-15.00 hours) and afternoon (15.00-18.00 hours). Blood pressure was monitored by an ambulatory blood pressure device during the whole 26 h period. Each urine sample was used to measure urinary sodium excretion and glomerular filtration rate (creatinine clearance). Blood pressure, heart rate, urinary sodium excretion and glomerular filtration rate recorded in the daytime were higher than those measured during the night-time. A significant positive correlation between mean blood pressure and urinary sodium excretion was found during the night, over the whole 26 h period, and during two subperiods of the daytime: quiet wakefulness and the post-prandial period. The coefficient of the pressure-natriuresis curve was significantly decreased by postural changes. We conclude that, in normotensive subjects, blood pressure and urinary sodium excretion are coupled in the short term. The assumption of an upright posture can mask this relationship, presumably by activating neurohumoral factors.

Glucocorticoids Induce Nondipping Blood Pressure by Activating the Thiazide-Sensitive Cotransporter

“…Clinical studies show that the day:night variation in BP is strongly correlated with renal sodium excretion. 9 The kidney is an important long-term regulator of BP and impaired pressure natriuresis may contribute to nocturnal hypertension 10 : BP remains elevated during sleep to facilitate sodium excretion and maintain 24-hour sodium balance. 11 , 12 Certainly, hypertensive and prehypertensive patients have a blunted day:night pattern of sodium excretion and excrete a greater fraction of their daily output at night.…”

Salty taste thresholds and preference in patients with chronic kidney disease according to disease stage: A cross‐sectional study

“…First, the two most widely used methods for evaluating sodium intake are 24‐hour urine sodium collection and dietary recall. The results of the one‐time spot urine sodium method may be biased by circadian variations in the blood sodium concentrations in the general population and in CKD patients . To compensate for this potential limitation, we evaluated the mean of the three most recent spot urine sodium concentrations to estimate the daily sodium intake in CKD patients.…”

Nocturnal Sodium Excretion, Blood Pressure Dipping, and Sodium Sensitivity

“…The authors concluded that the pressure-natriuresis relationship is blunted during upright posture, possibly because of the activation of neurohumoral systems. 8 Staessen et al 9 also observed that both systolic and diastolic blood pressure correlate with sodium excretion only during sleep. Staessen et al 10 went on to show that office systolic and diastolic blood pressures also correlated positively with nighttime sodium excretion, and Dyer et al 11 found the same relationship using a night/day sodium excretion ratio.…”