Evaluation of total body water in canine breeds by single-frequency bioelectrical impedance analysis method: specific equations are needed for accuracy.

BACKGROUND: Equations based on single-frequency bioelectrical impedance analysis at 50 kHz for determination of total body water content (TBW) have been previously validated in healthy non-sedated beagle dogs. We investigated whether these equations are predictive of TBW in various canine breeds by comparing the results of these equations with TBW values evaluated directly by deuterium oxide (D2O) dilution. METHODS: Total body water content of 13 healthy adult pet dogs of various breeds was determined directly using D2O dilution and indirectly using previous equations based on values obtained with a portable bioelectric impedance device. Paired Student's t-tests were used to compare TBW obtained by single-frequency bioelectrical impedance analysis and D2O dilution. A p-value of <0.05 was considered statistically significant for all analyses. RESULTS: Significant differences were observed between TBW determined by the reference method and the values obtained with both predictive equations. CONCLUSIONS: The proposed equations including single-frequency bioelectrical impedance analysis parameters validated at 50 kHz in healthy adult beagles need to be modified including morphological parameters such as body size and shape in a first approach. As in humans, morphological-specific equations have to be developed and validated.

Indirect prediction of total body water content in healthy adult Beagles by single-frequency bioelectrical impedance analysis.

OBJECTIVE: To develop equations for prediction of total body water (TBW) content in unsedated dogs by combining impedance (resistance and reactance) and morphological variables and to compare the results of those equations with TBW content determined by deuterium dilution (TBW(d)). ANIMALS: 26 healthy adult Beagles. PROCEDURES: TBW content was determined directly by deuterium dilution and indirectly with equations developed from measurements obtained by use of a portable bioelectric impedance device and morphological variables including body length, height, weight, and thoracic and abdominal circumferences. RESULTS: Impedance and morphological data from 16 of the 26 dogs were used to determine coefficients for the following 2 equations: TBW(1) = -0.019 (BL(2)/R) + -0.199 (RC + AC) + 0.996 W + 0.081 H + 12.31; and TBW(2) = 0.048 (BL(2)/R) + -0.144 (RC + AC) + 0.777 W + 0.066 H + 0.031 X + 7.47, where AC is abdominal circumference, H is height, BL is body length, R is resistance, RC is rib cage circumference, W is body weight, and × is reactance. Results for TBW(1) (R(2)(1) = 0.843) and TBW(2) (R(2)(2) = 0.816) were highly correlated with the TBW(d). When the equations were validated with data from the remaining 10 dogs, the respective mean differences between TBW(d) and TBW(1) and TBW(2) were 0.17 and 0.11 L, which equated to a nonsignificant underestimation of TBW content by 2.4% and 1.6%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that impedance and morphological data can be used to accurately estimate TBW content in adult Beagles. This method of estimating TBW content is less expensive and easier to perform than is measurement of TBW(d), making it appealing for daily use in veterinary practice.