Outcomes and predictors of skin sodium concentration in dialysis patients.

Background: Sodium-23 magnetic resonance imaging ( ²³ Na MRI) allows the measurement of skin sodium concentration ([Na ⁺ ]). In patients requiring dialysis, no data are available relating to the clinical outcomes associated with skin sodium accumulation or the determinants of increasing deposition.
Methods: This was an exploratory, observational study of adult hemodialysis (HD) and peritoneal dialysis (PD) patients. Participants underwent skin [Na ⁺ ] quantification with leg ²³ Na MRI at the study's beginning. Outcomes of interest were all-cause mortality and composite all-cause mortality plus major adverse cardiovascular events. Cumulative total and event-free survival were assessed using the Kaplan-Meier survival function after stratification into skin [Na ⁺ ] quartiles. Cox proportional hazards regression was used to model the association between skin [Na ⁺ ] and outcomes of interest. Multiple linear regression was used to model the predictors of skin [Na ⁺ ].
Results: A total of 52 participants (42 HD and 10 PD) underwent the study procedures. The median follow-up was 529 days (interquartile range: 353-602). Increasing skin [Na ⁺ ] quartiles were associated with significantly shorter overall and event-free survival (log-rank χ ² (1) = 3.926, log-rank χ ² (1) = 5.685; P for trend <0.05 in both instances). Skin [Na ⁺ ] was associated with all-cause mortality {hazard ratio (HR) 4.013, [95% confidence interval (95% CI) 1.988-8.101]; P < 0.001} and composite events [HR 2.332 (95% CI 1.378-3.945); P < 0.01], independently of age, sex, serum [Na ⁺ ] and albumin. In multiple regression models, dialysate [Na ⁺ ], serum albumin and congestive heart failure were significantly associated with skin [Na ⁺ ] in HD patients ( R ² _adj  = 0.62).
Conclusions: Higher skin [Na ⁺ ] was associated with worse clinical outcomes in dialysis patients and may represent a direct therapeutic target.
(© The Author(s) 2022. Published by Oxford University Press on behalf of the ERA.)