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Kidney Week

Abstract: SA-PO1063

Differential Sodium Ion Distribution in Muscle and Skin and Its Relationship to Hydration Status in Advanced CKD

Session Information

  • Na+, K+, Cl-
    November 04, 2017 | Location: Hall H, Morial Convention Center
    Abstract Time: 10:00 AM - 10:00 AM

Category: Fluid, Electrolytes, and Acid-Base

  • 703 Na+, K+, Cl- Basic

Authors

  • Mitsides, Nicos, Central Manchester University Hospitals NHS Foundation Trust, Manchester, United Kingdom
  • Mchugh, Damien J., The University of Manchester , Manchester, United Kingdom
  • Alderdice, Jane, Central Manchester University Hospitals NHS Foundation Trust, Manchester, United Kingdom
  • Swiecicka, Agnieszka, The University of Manchester , Manchester, United Kingdom
  • Brenchley, Paul E., Central Manchester University Hospitals NHS Foundation Trust, Manchester, United Kingdom
  • Parker, Geoff J M, The University of Manchester , Manchester, United Kingdom
  • Mitra, Sandip, Central Manchester University Hospitals NHS Foundation Trust, Manchester, United Kingdom
Background

Body sodium (Na) excess is an important determinant of cardiovascular risk in chronic kidney disease(CKD). Its effect is mediated, predominantly, through extracellular fluid (ECW) expansion. Although ECW is assumed to be a homogenous isotonic compartment, the relative proportions of water & Na ions in different tissue is unclear in CKD. We aim to quantify Na concentration in muscle(M) and subcutaneous(SC) tissue in relation to hydration states in advanced CKD.

Methods

Na ionic concentration was measured using a 3T MRI scanner & a dual-tuned 1H/23Na coil. The lower leg of 8 healthy controls(HC) & 20 CKD stage 5 patients(eGFR<15 ml/min, not on dialysis) was imaged & the M & SC Na concentration derived using saline calibration phantoms. Overhydration index(OH), ECW, intracellular(ICW) & total body water(TBW) was assessed using multifrequency bioimpedance spectroscopy(BIS). Blood Pressure(BP) was assessed by 24hr ambulatory monitoring & Na balance calculated using 3 day food diary & 24 hr urine Na measurements.

Results

The HC & CKD cohorts were similar in age(HC: 50±14.3yr;CKD 53±9.3yr;p=0.60) & sex(50% male) but the CKD cohort had significantly higher comorbidity (Charlson Index:HC 1.0 v CKD 3.0;p<0.01). The MR derived M Na concentrations were not different between the 2 groups (CKD 24.9±5.5mmol/L;HC 23.1±2.7mmo/L,p=0.38). However, CKD participants had higher SC Na concentration than HC(CKD 25.8±10.2mmol/L;HC 19.5±5.0mmol/L,p=0.04). M Na was strongly correlated to BIS measured ECW volume(ECW/TBW:r=0.502,p=0.01). Higher M Na was also associated with increased ECW/ICW ratio(r=0.533,p<0.01) & higher systolic BP(r=0.449,p=0.02). Both M & SC Na correlated with OH(M: r=0.536,p<0.01;SC:r=0.452,p=0.02). Baseline Na intake was 94.9±32.3mmol/24hr for CKD & 113.1±46.9mmol/24hr for HC(p=0.23) while urine Na excretion was 109.5±41.7 & 171.3±170.5 mmol/24hr respectively(p=0.98).

Conclusion

The distribution of Na ions appears to be heterogenous in body tissues. In M, Na appears to be accompanied by water (osmotically active) & closely linked to ECW expansion. On the other hand, the higher SC Na concentration seen in CKD is dissociated from ECW content & BP, implying an alternative pathophysiology, unrelated to volume homoeostasis, & possibly linked to CKD & higher comorbidity.

Funding

  • Clinical Revenue Support