Outcomes and predictors of skin sodium concentration in dialysis patients

Outcomes and predictors of skin sodium concentration in dialysis patients

  • Post category:Journal Update
  • Reading time:5 mins read

Introduction

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). Out of 42 HD patients, 8 were receiving an individualized dialysate [Na+] prescription (median, range: 138 mmol/L, 135–145); 17 patients were receiving a dialysate [Na+] prescription of 137 mmol/L and 17 patients were receiving a dialysate [Na+] prescription of 140 mmol/L. Dialysate [Na+] distribution according to skin [Na+] quartiles is shown in Figure 1.

Increasing skin [Na+] quartiles were associated with significantly shorter overall and event-free survival (log-rank x2(1) = 3.926, log-rank x2(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 (R2adj = 0.62). The results of the multiple linear regression analysis are summarized in Table 1

Conclusion

In conclusion, higher skin [Na+] (as quantified with 23Na MRI) was associated with worse clinical outcomes in dialysis patients. Although potential unaccounted confounding effects may be at play, these findings suggest sodium balance may play an important role in the care of dialysis patients, from both a traditional view (with expansion of extracellular volume) and as a function of our evolving understanding of water-free sodium accumulation within tissues.

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