Electrical impedance and haematocrit of human blood with various anticoagulants

The relationship between the electrical impedance parameters and the haematocrit of normal human blood has been determined at 37 degrees C in the haematocrit range of 20-60% for four types of anticoagulant: ACD, EDTA, sodium heparin and buffered sodium citrate. For plasma resistance R_p and interior resistance R_i, the measured data could be fitted by both the exponential expression and the Maxwell-Fricke expressions, R_p=a/(1-h)+b and R_i=a/h+b, where a and b are constants and h is the haematocrit expressed as a decimal. The membrane capacitance C_m was found to be directly proportional to the haematocrit and could be normalized to 100% haematocrit by the Fricke formula, C₁₀₀=C_m/(1- rho _p/R_p), where rho _p is the resistivity of plasma. Observed differences for R_p and C, among samples with various anticoagulants indicate that the type of anticoagulant influences the electrical properties of the red cells and the plasma.