Objective: Tissue sodium accumulation has been implicated in the pathophysiology of hypertension. In the skin, sodium accumulation may serve as an adaptive response to either chronic dehydration or high salt intake, reducing transepidermal water loss (TEWL) by increasing cutaneous vascular resistance, potentially leading to hypertension. This study aims to investigate the relationship between skin sodium content, blood pressure and skin water balance in patients with chronic kidney disease (CKD), who are characterized by tissue sodium accumulation. Design and method: Twenty-three CKD patients (i.e. kidney function (eGFR) 15-60 ml/min/1.73m2) underwent 23Na and 1H-MRI of the lower leg in a 7-tesla MR system. Skin and muscle sodium content was quantified through manual segmentation of both compartments, using a calibration curve derived from vials containing known sodium concentrations. TEWL was assessed using the Tewameter® TM Hex. Fluid status was measured using bioimpedance spectroscopy. Associations between tissue sodium content, TEWL, blood pressure and clinical characteristics were analyzed using linear regression and Wilcoxon signed-rank tests. Results: Mean age of the patients was 62±17 years, 43% were male and mean eGFR was 37±13 mL/min/1.73m2. The median skin and muscle sodium content were 16 12-22 mmol/L and 18 16-24 mmol/L, respectively. Skin (R2=0.39, p=0.001) and muscle (R2=0.24, p=0.019) sodium content showed a positive correlation with age (Figure 1). Males had a higher skin sodium content than females (19 16-24 vs. 12 10-14 mmol/L p=0.021), whereas muscle sodium content was similar (19 18-27 vs. 17 16-20 mmol/L, p=0.21). Skin sodium was positively associated with office systolic blood pressure (R2=0.26, p=0.012) and total body overhydration (R2=0.26, p=0.014). Tissue sodium content was not associated with TEWL. A higher 24-hour systolic blood pressure (R2=0.18, p=0.041) and lower eGFR (R2=0.17, p=0.050) were associated with lower skin water loss.Conclusions: We confirm the association between skin sodium content and age, sex, hydration status and blood pressure in CKD. Our data suggest that skin water balance is involved in blood pressure regulation in patients with CKD. These findings highlight the complex interplay between tissue sodium, fluid balance and blood pressure management in this population.
Simon et al. (Fri,) studied this question.