Article
Salt Consumption and 24-h Blood Pressure Profiling in Chronic Renal Failure
Salzkonsum und Hypertonieklassifikation durch 24-h Blutdruckmessung bei chronischer Niereninsuffizienz
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Published: | November 11, 2004 |
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Outline
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Aim
Patients with chronic renal failure lack capacity to excrete osmolytes, easily retain fluids and react with hypertension upon a salt load. The value of 24h ambulatory blood pressure measurement (ABPM) compared with office BP to correctly detect and classify hypertension in this context remains unclear.
Methods
In a retrospective survey, we analyzed 142 consecutive and otherwise unselected out-patients with chronic renal failure and 24h ABPM attending our nephrology department. Serum creatinine (CREA), daily Na, K and Ca excretion, body mass index, urinary volume and serum electrolytes were analyzed. Patients had been instructed to comply with a reduced salt diet of <6 g/d. Antihypertensive medication was adjusted to a BP goal <130/90 mm Hg.
Results
Mean age was 50 13 y, mean CREA was 213 183 mol/L, 35% were female, 19,7% diabetics, 54% had chronic glomerulonephritis, all were on antihypertensive medication and 62% had >2 such drugs. Mean daily excretion of Na+ , K+ and Ca2+ was 210, 65 and 2.8 mmol, respectively. Mean office BP was 140/81 mm Hg and not different from day ABP, without a sex difference. Men ate about 3 g/d more salt than women. Daily urinary volume (2518 690 ml/d) correlated with 24h Na excretion (r=0.37, p<0.01) but not with CREA. There was no difference in Na excretion, urinary volume and serum electrolyte concentrations between ABPM-dippers (12%) and non-dippers or when patients were classified according to WHO hypertension grades (p=NS). CREA correlated with 24h systolic ABP values (r=0.31, p<0.05) but not with office BP. ABPM reclassified hypertension correctly in about 1/5 of the patients depending on salt intake compared with office BP.
Conclusion
Average daily salt consumption was 2-3 times above the recommended limit, did not differ between hypertension grades and imposed an avoidable osmotic and volume load in patients with chronic renal disease and hypertension. ABPM helped reduce misclassifications of hypertension.