Estimation of total body water from routine urea kinetics
Bosticardo, G.M.; Alloatti, S.; Vidano, E.; Cestonaro, G.; Gavassa, L.; Scagliola, C.; Giacchino, F.
Minerva Urologica e Nefrologica 50(1): 115-119
1998
ISSN/ISBN: 0393-2249 PMID: 9578671 Document Number: 493950
The comparison of total body water obtained by Watson formula with results of bioelectrical impedance (BIA) shows a fair approximation (Delta% = 1.0 +/- 8.45). However, when compared to other literature formulas the BIA values are higher (8 divided by 23%), and this discrepancy needs further analysis. Urea kinetics was computed using as input data for distribution volume both the Watson anthropometrical and the BIA TBW values: the clearance results do not differ significantly (Delta% = 0.74 +/- 8.35). The Kt/V index results are nearly identical (Delta% = 0.12 +/- 1.17), due to a mathematical loop: a wrong input of volume induces a comparable error of the clearance result, while their ratio is unchanged. For practical routine to monitoring dialysis adequacy the Watson anthropometrical formula has proven as a satisfactory simple approach. Periodical BIA determination provides useful informations mainly when the anthropometrical estimation are doubtful and the comparison of data may increase the kinetic reliability.