Abstract
Up to now TBW is generally determined on the basis of measurements of D2O concentration in blood after an i.v. dose of D2O. We wondered if TBW could be determined on the basis of D2O concentrations in urine after giving D2O orally. Eight experiments were carried out in 6 preterm neonates (gest. age: 31.5 wk±3.5, birthweight: 1855 g±516, mean±SD). The D2O concentrations were measured in every portion of urine voided within 24 h (on the average 16 portions) after giving D2O (2 ml/kg) orally. In 5 experiments D2O concentrations were also determined in blood. TBW was calculated after extrapolating the regression line after the equilibration period (on the average 5 h) to time 0. After equilibration, the D2O concentration in urine decreased linearly (r= -0.99±0.01). Using D2O concentration in urine TBW was on the average 1.5% lower than calculated with D2O concentrations in blood.
Conclusion: TBW can be measured on the basis of D2O in urine after giving D2O orally. Considering the high correlation coefficient, we suggest that TBW can be calculated using only 3 portions of urine collected between 6 to 24 h after giving D2O orally.
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Hof, P., Baarsma, R., Zijlstrs, W. et al. RELIABILITY OF NON-INVASIVE MEASUREMENT OF TOTAL BODY WATER (TBW). Pediatr Res 26, 523 (1989). https://doi.org/10.1203/00006450-198911000-00145
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DOI: https://doi.org/10.1203/00006450-198911000-00145