A comparison of two tests for the assessment of blood pressure responses to sodium.

In order to assess the congruity of two different methods for the characterization of blood pressure responsivity to alterations in sodium and extracellular fluid volume balance, we studied 40 normotensive and hypertensive humans. All subjects were initially studied with a protocol of rapid sodium and volume expansion induced by intravenous administration of 0.9% saline (2 L over 4 h) followed by a day of sodium and volume depletion achieved by a low (10 mmol) sodium diet and three 40 mg oral doses of furosemide. Subsequently the subjects underwent a dietary protocol consisting of 5 days of a high (> or = 200 mmol/da) sodium diet followed by 7 days of a low (< or = 15 mmol/day) sodium diet. Blood pressure measurements as well as urinary sodium, potassium, and creatinine excretion measurements were made daily in both studies. A significant (P < .01) correlation was observed between the blood pressure responses to the separate techniques in the same individual. However, not all subjects responded in a similar qualitative fashion to the two maneuvers. The discrepancy was more frequent among subjects having a salt-resistant response to the rapid protocol. The renin response to sodium and volume depletion induced by the low sodium diet and furosemide correlated significantly (P < .001) with the subsequent blood pressure response to the low sodium diet. Subjects defined as salt-sensitive differed from the salt-resistant group by more sluggish renal adaptation to dietary sodium restriction. These findings demonstrate the congruity of two different approaches for the assessment of salt responsivity of blood pressure in humans.(ABSTRACT TRUNCATED AT 250 WORDS)