Shear Rate and Temperature Dependent Characterization of Blood-Mimicking Fluids for Blood Warming Device Application.

During emergency transfusion, stored whole blood at 1-6°C must be rapidly warmed to 36-38°C using blood warming devices. However, device validation commonly relies on Newtonian crystalloid intravenous fluids with a viscosity of 1 mPa·s, whereas whole blood exhibits temperature-dependent, shear-thinning rheology with viscosities of 3.5-4.5 mPa·s at 37°C. This discrepancy introduces systematic errors in performance evaluation. To address this gap, this research study characterized three blood-mimicking fluids (BMFs), including glycerol-water solutions of 22-50% w/w, egg whites, and TrueClot across temperatures of 5-40°C and shear rates of 5-100 s⁻¹. Among the tested fluids, TrueClot most closely resembled blood in overall rheological properties. However, TrueClot demonstrated abnormal phase separation at temperatures below 10°C, with a 28% drop in viscosity from 55 ± 4 to 39.6 ± 0.5 mPa·s over just 2°C, limiting its use at refrigerated storage temperatures. At shear rates ≥ 100 s⁻¹, 50% glycerol-water solutions produced viscosity values closest to reported whole blood values. Based on the rheological profiles obtained, it is inferred that at shear rates < 100 s⁻¹, diluted TrueClot at temperatures higher than 10°C or modified egg whites with xanthan gum at 5-40°C may provide suitable shear-thinning properties, though experimental validation of these modified solutions is required. Two mathematical models, including the Casson model with Apostolidis and Beris parametrization and a combined shear-temperature power law model, were developed to predict viscosity values that correlate well with the experimental results.