Sodium Output—Blood Pressure Relationships and Their Modification by Treatment

Abstract

The relation of urinary Na excretion to blood pressure under various conditions was studied in 75 normotensive and hypertensive subjects. The 24 hour rate of Na excretion was significantly correlated with both the basal rate and the rate under 5% saline load. The average basal rate did not differ significantly from the average 24 hour rate, suggesting that the basal rate may be used as an index of the overall intake and output in groups of subjects under conditions which indicate the existence of Na balance. The average 24 hour output of the hypertensive subjects prior to treatment was about 35% higher than the normotensive output Since all subjects were on self-selected diets and had shown stable weights during this period of observation, the inference was made that the Na appetite of the hypertensive group was increased as well. The Na output under load was found to be well correlated with the mean blood pressure. This relationship persisted when the blood pressure of the hypertensive patient was lowered by medical or surgical treatment. Only 8% of the treated hypertensive patients showed loading responses above the highest control value, as compared with 33% of the group prior to treatment These 8% were comprised of individuals whose blood pressure was not materially reduced as a result of treatment.