Measurement of Sweat Sodium Concentration in Patients With Chronic Kidney Disease

Sweat sodium concentration

It has been shown that excretion of sodium and water through the skin in the form of sweat
 represents a regulatory mechanism of electrolyte- and fluid balance. Since patients with
 chronic kidney disease (CKD) exhibit increased skin sodium content, we investigated the
 feasibility of sweat testing as a novel experimental tool to a more complete assessment of
 fluid- and sodium homeostasis.
 
 In this cross-sectional feasibility study, we applied pilocarpine iontophoresis to induce
 sweat testing in 58 patients across various stages of CKD including patients after kidney
 transplantation as well as a healthy control cohort (n=6) to investigate possible effects of
 CKD and transplantation status on sweat rate and sodium concentration. Due to non-linear
 relationships, we modeled our data using polynomial regression.
 
 Decline of kidney function showed a significant association with lower sweat rates: adj R²=
 0.2278, F(2, 61) = 10.29, p = 0.000141. Sweat sodium concentrations were increased in
 moderate CKD, however this effect was lost in end stage renal disease: adj R² = 0.3701, F(4,
 59) = 10.26, p = 2.261e-06. We observed higher sweat weight in males compared to females.
 
 Diagnostic sweat analysis represents an innovative and promising noninvasive option for more
 thorough investigation of sodium- and fluid homeostasis in CKD patients. Lower sweat rates
 and higher sweat sodium concentrations represent a unique feature of CKD patients with
 potential therapeutic implications.