NDT Advance Access published online on March 8, 2008
Nephrology Dialysis Transplantation, doi:10.1093/ndt/gfn045
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A non-invasive, on-line deuterium dilution technique for the measurement of total body water in haemodialysis patients
1 Department of Nephrology, University Hospital of North Staffordshire, Stoke-on-Trent, ST4 7LN
2 Institute of Science and Technology in Medicine, Keele University Medical School (Hartshill Campus), Thornburrow Drive, Hartshill, Stoke-on-Trent, ST4 7QB, UK
3 J. Heyrovsk
Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Czech Republic
4 School of Graduate Entry Medicine and Health, University of Nottingham, Uttoxeter Road, Derby, DE22 2NE
Correspondence and offprint requests to: Simon J Davies, Department of Nephrology, University Hospital of North Staffordshire, Princes Road, Hartshill, Stoke-on-Trent ST4 7LN, UK. Tel: +44-1782-554164; Fax: +44-1782-620759; Email: simondavies1{at}compuserve.com
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Abstract |
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Background. Despite its importance, total body water (TBW) is usually estimated rather than measured due to the complexity of isotope dilution methods. The aim of this study was to demonstrate the applicability in haemodialysis (HD) patients of a recently developed on-line breath test, previously validated in healthy subjects, that uses the gold standard deuterium dilution method to measure TBW. In particular we wished to show that a pre-dialysis estimation was as good as a post-dialysis equilibrated measurement in order to avoid patients needing to remain behind after dialysis treatment.
Methods. The dispersal kinetics of breath HDO, measured using a flowing afterglow mass spectrometer (FA-MS) following ingestion of D2O immediately post-dialysis, were determined in 12 haemodialysis patients and used to calculate the absolute TBWPostHD after full equilibration. TBWPreHD was then determined from breath samples taken immediately prior to the next dialysis. This measurement was adjusted for the interdialytic weight change and urine output (TBWPreHD-adjusted) and compared to the TBWPostHD. The accuracy and precision of FA-MS was also assessed using known concentrations of deuterium-enriched water samples.
Results. Mean TBWPostHD was 50.0 ± 9.3 L and TBWPreHD-adjusted was 50.7 ± 9.0 L. They were highly correlated (R = 0.99, P < 0.001) with a CV of 2.6%. The mean difference was +0.74 L (SEM 0.35, 95% CI –0.03 to 1.51 L, P = 0.059), compatible with a daily insensible loss of 0.37 L. Accuracy and precision of FA-MS were comparable to the previous validation work.
Conclusions. This non-invasive adaptation of the D isotope dilution method for determining TBW can be applied to haemodialysis patients who show deuterium equilibration kinetics identical to normal subjects; a pre-dialysis estimation may be used to determine TBW, and so avoiding the necessity to remain behind after dialysis making this suitable for application in the clinical setting.
Keywords: flowing after-glow mass spectrometer (FA-MS); body composition; deuterium dilution; total body water; volume of urea distribution
Received for publication: 27. 7.07
Accepted in revised form: 22. 1.08
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  C. Chan, C. McIntyre, D. Smith, P. Spanel, and S. J. Davies Combining Near-Subject Absolute and Relative Measures of Longitudinal Hydration in Hemodialysis Clin. J. Am. Soc. Nephrol., November 1, 2009; 4(11): 1791 - 1798. [Abstract] [Full Text] [PDF]
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