Extracorporeal circulation induces pronounced effects on haemostasis and rheology. To study these, an ex vivo simulation model is an attractive alternative but often requires large amounts of blood. We sought to create a miniaturized roller pump circuit requiring minimal amounts of blood and to test if the circuit could be used to compare coagulation, platelet function and blood rheology between a dextran-based and a crystalloid-based priming solution.

A miniaturized roller pump circuit requiring only 27 ml of blood was created. Blood samples from 8 cardiac surgery patients were mixed with either a dextran-based or a crystalloid-based solution and circulated for 60 min. Coagulation was assessed by rotational thromboelastometry, and platelet function by impedance aggregometry and flow cytometry, before and at 5 and 60 min of circulation.

A time-dependent impairment of coagulation was observed in both groups. Maximum clot firmness was lower with dextran-based than with crystalloid-based priming at 5 min (HEPTEM 37 ± 4 vs 43 ± 4 mm, P < 0.001; EXTEM 37 ± 4 vs 43 ± 4 mm, P < 0.001; FIBTEM 3 ± 2 vs 9 ± 2 mm, P < 0.001) and at 60 min (HEPTEM 29 ± 9 vs 38 ± 5 mm, P < 0.001; EXTEM 30 ± 7 vs 39 ± 5 mm, P < 0.001; FIBTEM 3 ± 2 vs 8 ± 3 mm, P = 0.002). The EXTEM clotting time was longer with dextran-based solution at 5 (109 ± 19 vs 63 ± 7 sec, P < 0.001) and at 60 min (176 ± 72 vs 73 ± 7 sec, P = 0.004).

The novel miniaturized roller pump circuit can be used to mimic extracorporeal circulation for selected research questions. Dextran-based priming caused a significant impairment in haemostasis compared with a standard crystalloid solution.