Outcomes and predictors of skin sodium concentration in dialysis patients

Fabio R Salerno; Alireza Akbari; Sandrine Lemoine; Guido Filler; Timothy J Scholl; Christopher W McIntyre

doi:10.1093/ckj/sfac021

Outcomes and predictors of skin sodium concentration in dialysis patients

Clin Kidney J. 2022 Jan 28;15(6):1129-1136. doi: 10.1093/ckj/sfac021. eCollection 2022 Jun.

Authors

Fabio R Salerno¹, Alireza Akbari², Sandrine Lemoine², Guido Filler², Timothy J Scholl¹, Christopher W McIntyre¹

Affiliations

¹ Department of Medical Biophysics, Western University, London, ON, Canada.
² The Lilibeth Caberto Kidney Clinical Research Unit, London Health Sciences Centre, London, ON, Canada.

Abstract

Background: Sodium-23 magnetic resonance imaging (²³Na 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 ²³Na 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 χ²(1) = 3.926, log-rank χ²(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 (R² _adj = 0.62).

Conclusions: Higher skin [Na⁺] was associated with worse clinical outcomes in dialysis patients and may represent a direct therapeutic target.

Keywords: chronic hemodialysis; clinical outcomes; magnetic resonance imaging; peritoneal dialysis; sodium.