A blood mimicking fluid for clot-detection experiments with ultrasound

Purpose: Monitoring of coagulation tendencies is important during many therapies, e.g. during dialysis or heart surgery with extracorporeal blood circulation. The monitoring could be done with ultrasound which can help physicians to make informed decisions on treatments. To ensure safety and to get administrative approval of the ultrasound measurement lots of experiments are necessary. Therefore a fluid that mimics rheological as well as acoustical properties of blood as closely as possible is necessary.

Material & methods: We want to model the early stages of coagulation and therefore adapted a recipe of a blood mimicking fluid (BMF). The constituents of the BMF are polyamide particles with diameters 5 µm as erythrocyte and 20 µm to 60 µm as small clot mimics. Surfactant is added to suspend the particles. Water, glycerine, and dextran mimic the blood plasma. Their amount was adjusted to represent rheological and acoustical properties of blood as closely as possible. Experiments were performed to examine the fluids properties. Among others, viscosity was measured with a rheometer, speed of sound and the absorption coefficient in pulse-echo-mode, and density with a pycnometer.

Results: The haematocrit of the BMF is up to 30 Vol% (polyamide particles). Viscosity and density strongly agree with that of blood, speed of sound is somewhat higher (1680 m/s), and the attenuation coefficient is much stronger than that in blood. The latter is due to different impedances of polyamide particles and erythrocytes.

Conclusions: It is essential to find a blood mimicking fluid that closely reproduces rheological, acoustical and to some extent mechanical blood properties in larger vessels and during coagulation. Our BMF overcomes difficulties as suspensibility at higher haematocrit concentrations or air bubbles in the solution. Concerning all aspects, this recipe is an adequate mimic for research to be used at higher haematocrit values.