[Measurement of the specific electrical resistance of the blood (rho) and its determination mathematically in dogs].

The role of specific electric resistance of blood (rho) in determining systolic cardiac volume by impedance plethysmography is discussed. It is pointed out that the known five mathematical equations for rho estimation by the hematocrit (Hct) and the temperature (T0) differ from one another and are moreover good for humans, but not for experimental animals. A suitable equipment and technique for direct (in vitro) measurement of rho is suggested. The obtained results enabled to deduce a mathematical dependence, allowing to determine the specific electric resistance of blood (rho) in dogs with sufficient accuracy, on the basis of the hematocrit and the temperature. The adequacy of this mathematical dependence for determination of rho in dogs has been confirmed by control studies.