Associação da relação sódio/potássio urinários com alterações vasculares estruturais e funcionais em pacientes hipertensos não diabéticos

Abstract

There are some evidences pointing out that high sodium (Na) and low potassium (K) intake are associated with increased prevalence of hypertension, structural and functional changes in the vascular wall. Studies aiming to associate the Na/K ratio with hypertension use 24-hour urinary excretion as a daily marker of ingestion. The objective of this study was to evaluate the association between urinary Na/K ratio and structural and functional vascular alterations in non-diabetic hypertensive patients. A cross-sectional study was performed with hypertensive patients of both sexes, aged between 40 and 70 years, using hydrochlorothiazide as antihypertensive medication. Selected patients were submitted to clinical and nutritional evaluation, blood pressure oscillometric measurement, biochemical evaluation, 24-hour urine sample collection, and assessment of pulse wave velocity (PWV), central hemodynamic parameters and cutaneous microvascular reactivity. The participants (n=72) were divided according to the tertile of 24-hour urinary Na/K ratio. Each group contained 24 patients, the first tertile (T1) was defined as urinary Na/K ratio < 2.69; the third tertile (T3) &#8805; 4.39; and the second tertile (T2) between them. The mean age was 58 years and 61% were women. Results were expressed as mean ± standard deviation or median (interquartile range). The systolic blood pressure was higher in T2 (133±9 vs 140±9 mmHg, p=0.029) and mean arterial pressure in T3 as compared to T1 (98±8 vs 104±9 mmHg, p=0.028). No significant differences were found in laboratory parameters, except for C-reactive protein (CRP), which presented higher values in T3 as compared to T1 [0.20(0.10-0.34) vs 1.19(0.96-1.42) mg/dl, p<0.001]. Proteinuria [95(82-113) vs 139(94-177) mg/24h, p=0.036] and 24-hour urinary Na/K ratio (1.89±0.58 vs 5.76±1.26, p<0.001) were higher in T3 compared to T1. Higher values in T3 was also observed for aortic systolic pressure (aoSP) [119(114-130) vs 135(125-147) mmHg, p=0.002], aortic pulse pressure (aoPP) [42(35-49) vs 46(43-59) mmHg, p=0.042] and carotid-femoral PWV (cf-PWV) (9.2±1.6 vs 11.1±1.5 m/s, p<0.001). The urinary Na/K ratio presented significant correlations with proteinuria (r=0.27, p=0.023), aoSP (r=0.41, p<0.001), aoPP (r=0.37, p<0.001), CRP (r=0.77, p<0.001), cf-PWV (r=0.41, p<0.001), PP amplification (r= -0,34, p=0.003) and cutaneous vascular conductance in post-occlusion reactive hyperemia (CVC-PORH) (r= -0.23, p=0.047). By multiple linear regression, it was detected an independent and significant association of cf-PWV with urinary Na/K ratio, aoSP with cf-PWV and CRP, and CVC-PORH with CRP. In conclusion, increased urinary Na/K ratio in non-diabetic hypertensive patients was associated with higher degree of inflammation, raised peripheral and central pressure levels, and changes suggestive of endothelial dysfunction and arterial stiffness.