• Sascha Gross-Hardt, Felix Hesselmann, Jutta Arens, Ulrich Steinseifer, Leen Vercaemst, Wolfram Windisch, Daniel Brodie, and Christian Karagiannidis.
• Department of Cardiovascular Engineering, Medical Faculty, Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Aachen, Germany.
• Crit Care. 2019 Nov 6; 23 (1): 348.

BackgroundExtracorporeal carbon dioxide removal (ECCO2R) uses an extracorporeal circuit to directly remove carbon dioxide from the blood either in lieu of mechanical ventilation or in combination with it. While the potential benefits of the technology are leading to increasing use, there are very real risks associated with it. Several studies demonstrated major bleeding and clotting complications, often associated with hemolysis and poorer outcomes in patients receiving ECCO2R. A better understanding of the risks originating specifically from the rotary blood pump component of the circuit is urgently needed.MethodsHigh-resolution computational fluid dynamics was used to calculate the hemodynamics and hemocompatibility of three current rotary blood pumps for various pump flow rates.ResultsThe hydraulic efficiency dramatically decreases to 5-10% if operating at blood flow rates below 1 L/min, the pump internal flow recirculation rate increases 6-12-fold in these flow ranges, and adverse effects are increased due to multiple exposures to high shear stress. The deleterious consequences include a steep increase in hemolysis and destruction of platelets.ConclusionsThe role of blood pumps in contributing to adverse effects at the lower blood flow rates used during ECCO2R is shown here to be significant. Current rotary blood pumps should be used with caution if operated at blood flow rates below 2 L/min, because of significant and high recirculation, shear stress, and hemolysis. There is a clear and urgent need to design dedicated blood pumps which are optimized for blood flow rates in the range of 0.5-1.5 L/min.

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