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Abstract: TH-PO448

Association of Blood Pressure with Urinary Sodium, Potassium, and Sodium/Potassium Ratio in CKD - The French CKD-REIN Cohort Study

Session Information

Category: Hypertension and CVD

  • 1401 Hypertension and CVD: Epidemiology, Risk Factors, and Prevention

Authors

  • Alencar de Pinho, Natalia, Inserm /CESP, Villejuif, France
  • Kabore, Jean, Institute for Research in Health Science, Ouagadougou, Burkina Faso
  • Drueke, Tilman B., Inserm /CESP, Villejuif, France
  • Laville, Maurice, Université de Lyon, Pierre-Bénite, France
  • Robinson, Bruce M., Arbor Research Collaborative for Health, Ann Arbor, Michigan, United States
  • Massy, Ziad, Ambroise Pare University Hospital and Inserm U1018 Eq5, Boulogne Billancourt/ Paris cedex, France
  • Stengel, Benedicte, Inserm /CESP, Villejuif, France
Background

The urinary sodium-to-potassium ratio (uNa/K) has been repeatedly shown to be more closely linked to blood pressure (BP) than urinary sodium or potassium excretion alone, both in general population and in patients with arterial hypertension. Whether this is also true for patients with CKD is unknown.

Methods

We assessed associations of BP with spot urine sodium/creatinine (uNa/Cr), potassium/creatinine (uK/Cr), and uNa/K in 1658 patients with CKD stages 3 or 4 under nephrology care. We used the mean of 2 office BP readings for analyses. Urinary Na, K, and creatinine concentrations were measured in second-void urine samples and expressed in mmol/L. Associations of BP with uNa/Cr, uK/Cr, and uNa/K modeled by 4-knot splines were assessed using generalized linear models adjusted for age, gender, eGFR, albuminuria, diabetes, heart failure, dyslipidemia, body mass index, and number of antihypertensive drugs.

Results

Median (IQR) age was 68 (59-76) years; most patients were men (65.3%), had CKD stage 3 (54.9%), and albuminuria (71.7%). Mean systolic (SBP) and diastolic (DBP) BP were 141 and 78 mm Hg, respectively. More than 90% of the patients had a history of arterial hypertension, and only 34% among them had controlled BP <140/90 mmHg. Median (IQR) uNa/Cr, uK/Cr, and uNa/K were 11.6 (7.9-16.3), 5.3 (4.1-7.0), and 2.2 (1.5-3.1), respectively. Spot uNa/Cr and uNa/K were positively associated with SBP (p 0.004 for both urinary indices) and with pulse pressure (p 0.002 and 0.019, respectively). The mean difference (β) in SBP between the highest and the lowest quartile (Q4-Q1) was 4.48 (95%CI 1.81-7.16) mmHg for uNa/Cr and 4.47 (95%CI 1.91-7.03) mmHg for uNa/K. Spot uK/Cr was not associated with any of the BP indices. The higher the quartile of uNa/K, but not of uNa/Cr, the higher the likelihood of uncontrolled (p 0.066) or apparently treatment resistant hypertension (p 0.033).

Conclusion

The positive association of urinary sodium, but not potassium, excretion with SBP and pulse pressure suggests a predominant role of sodium intake in determining BP level in many patients with CKD stages 3-4. In contrast with the general population, spot uNa/K does not appear to be more informative than uNa/Cr in such patients.