Analysis of the Difference in the Pressure-Natriuresis Relationship Based on the Class of Medication Using Spot Urine Tests in Hypertensive Patients

Objective: We estimated the daily sodium intake using a spot urine method in hypertensive patients, and investigated the differences in the pressure-natriuresis relationship depending on the type of medications and the involvement of renal function in this relationship. Methods: This study included 356 spot urine samples of hypertensive patients at our cardiology outpatient clinic. Daily sodium intake was estimated by the spot urine tests at the time of study enrolment. We examined the difference in the relationships among estimated daily sodium intake, mean blood pressure (mBP), and estimated glomerular filtration rate (eGFR) with each medication. Results: In multivariate analysis, the eGFR and mBP were significantly associated with estimated daily sodium intake. The slope of the pressure-natriuresis relationship was steeper in patients treated with renin-angiotensin system inhibitors (RAS-I) plus diuretics, and lower in patients treated with RAS-I plus calcium-channel blockers (CCB) than in those treated with CCB or who were not treated. eGFR was higher in patients with higher daily sodium intake than in those with lower daily sodium intake in association with higher mBP, except for patients treated with CCB alone. Conclusions: Estimated daily sodium intake in hypertensive patients was positively correlated with eGFR and mBP. The slope of the pressure-natriuresis relationship curve was different depending on the class of medication. In hypertensive patients with higher sodium intake, the relationship between mBP and eGFR may be important when selecting the type of medication.