TY - JOUR
T1 - Extracellular resistance is sensitive to tissue sodium status; implications for bioimpedance-derived fluid volume parameters in chronic kidney disease
AU - Mitsides, Nicos
AU - McHugh, Damien
AU - Swiecicka, Agnieszka
AU - Mitra, Roshni
AU - Brenchley, Paul
AU - Parker, Geoff J.M.
AU - Mitra, Sandip
N1 - Funding Information:
We would like to thank the clinical and technical staff at the participating units, the Manchester Renal Research and Transplant Laboratory and the University of Manchester Imaging Facilities for their help and support. The study was funded through a charitable grant from Kidneys for Life and an internal University of Manchester Magnetic Imaging Facilities grant for proof of concept imaging studies.
Funding Information:
Acknowledgements We would like to thank the clinical and technical staff at the participating units, the Manchester Renal Research and Transplant Laboratory and the University of Manchester Imaging Facilities for their help and support. The study was funded through a charitable grant from Kidneys for Life and an internal University of Manchester Magnetic Imaging Facilities grant for proof of concept imaging studies.
Publisher Copyright:
© 2019, The Author(s).
PY - 2020/2/1
Y1 - 2020/2/1
N2 - Multifrequency bioimpedance spectroscopy (BIS) is an established method for assessing fluid status in chronic kidney disease (CKD). However, the technique is lacking in predictive value and accuracy. BIS algorithms assume constant tissue resistivity, which may vary with changing tissue ionic sodium concentration (Na+). This may introduce significant inaccuracies to BIS outputs. To investigate this, we used 23Na magnetic resonance imaging (MRI) to measure Na+ in muscle and subcutaneous tissues of 10 healthy controls (HC) and 20 patients with CKD 5 (not on dialysis). The extracellular (Re) and intracellular (Ri) resistance, tissue capacitance, extracellular (ECW) and total body water (TBW) were measured using BIS. Tissue water content was assessed using proton density-weighted MRI with fat suppression. BIS-derived volume indices were comparable in the two groups (OH: HC − 0.4 ± 0.9 L vs. CKD 0.5 ± 1.9 L, p = 0.13). However, CKD patients had higher Na+ (HC 21.2 ± 3.0, CKD 25.3 ± 7.4 mmol/L; p = 0.04) and significantly lower Re (HC 693 ± 93.6, CKD 609 ± 74.3 Ohms; p = 0.01); Ri and capacitance did not vary. Na+ showed a significant inverse linear relationship to Re (rs = − 0.598, p < 0.01) but not Ri. This relationship of Re (y) and Na+ (x) is described through equation y = − 7.39x + 814. A 20% increase in tissue ionic Na+ is likely to overestimate ECW by 1.2–2.4L. Tissue Na+ concentration has a significant inverse linear relationship to Re. BIS algorithms to account for this effect could improve prediction accuracy of bioimpedance derived fluid status in CKD.
AB - Multifrequency bioimpedance spectroscopy (BIS) is an established method for assessing fluid status in chronic kidney disease (CKD). However, the technique is lacking in predictive value and accuracy. BIS algorithms assume constant tissue resistivity, which may vary with changing tissue ionic sodium concentration (Na+). This may introduce significant inaccuracies to BIS outputs. To investigate this, we used 23Na magnetic resonance imaging (MRI) to measure Na+ in muscle and subcutaneous tissues of 10 healthy controls (HC) and 20 patients with CKD 5 (not on dialysis). The extracellular (Re) and intracellular (Ri) resistance, tissue capacitance, extracellular (ECW) and total body water (TBW) were measured using BIS. Tissue water content was assessed using proton density-weighted MRI with fat suppression. BIS-derived volume indices were comparable in the two groups (OH: HC − 0.4 ± 0.9 L vs. CKD 0.5 ± 1.9 L, p = 0.13). However, CKD patients had higher Na+ (HC 21.2 ± 3.0, CKD 25.3 ± 7.4 mmol/L; p = 0.04) and significantly lower Re (HC 693 ± 93.6, CKD 609 ± 74.3 Ohms; p = 0.01); Ri and capacitance did not vary. Na+ showed a significant inverse linear relationship to Re (rs = − 0.598, p < 0.01) but not Ri. This relationship of Re (y) and Na+ (x) is described through equation y = − 7.39x + 814. A 20% increase in tissue ionic Na+ is likely to overestimate ECW by 1.2–2.4L. Tissue Na+ concentration has a significant inverse linear relationship to Re. BIS algorithms to account for this effect could improve prediction accuracy of bioimpedance derived fluid status in CKD.
KW - Bioimpedance
KW - CKD
KW - Sodium
UR - http://www.scopus.com/inward/record.url?scp=85067854099&partnerID=8YFLogxK
U2 - 10.1007/s40620-019-00620-3
DO - 10.1007/s40620-019-00620-3
M3 - Article
C2 - 31214996
AN - SCOPUS:85067854099
SN - 1121-8428
VL - 33
SP - 119
EP - 127
JO - Journal of Nephrology
JF - Journal of Nephrology
IS - 1
ER -