The first aim was the development of a human blood miniature mock-loop system consisting of 2 identical extracorporeal circuits, which enable systematic head-to-head comparisons of test substances. In a second step, we evaluated the suitability of the mock-loop system, by comparing 2 different brands of heparin (ROTEXMEDICA vs B.BRAUN), which have showed different anticoagulation capacities in the clinic.
For 1 experiment (18 in total), blood of the same healthy human donor was divided into 2 portions (2 × 50 ml), heparinized with 37.5 IU⋅ml−1 of the competing test substances and diluted to a haematocrit value of 20–25%. Each mock loop was filled with 70 ml, and in vivo heparin degradation was simulated in 3 different groups by protamine application, representing 0%, 50% and 100% heparin antagonization. At baseline, 5, 60, 120, 240 and 360 min, blood samples were taken to perform thromboelastometry, flow cytometry, haemolysis and general haemostasis analysis.
Blood pressure, blood flow and blood temperature within the loops remained stable for 6 h in all groups. After 6 h, in the 100% antagonized ROTEXMEDICA heparin group, significantly increased haemolysis (148.7 ± 80 mg⋅dl−1 vs 57.5 ± 15.8 mg⋅dl−1), activated platelets (8 ± 3.8% vs 3.3 ± 0.7%), D-dimers (7376 ± 7144 ng ml−1 vs 576.2 ± 190 ng ml−1) and fulminant blood clots were detected.
Our in vitro system is suitable for the detection of reduced anticoagulation capacity of a test drug, which was reported in vivo previously.