Optimized Veno-Venous Bypass with the Affinity Pump

Veno-venous bypass (VVBP) is increasingly used to avoid acute venous hypertension and low cardiac output after clamping the vena cava. Air embolism upon accidental decannulation of the inflow line and endothelial damage due to suction of the blood collecting cannula to the vessel wall are known complications specific to the currently used roller and centrifugal pumps, because they generate negative pressure at the inflow site of the pump. The Affinity pump has a unique chamber design with an occlusive segment, that collapses in low filling states preventing negative pressure at the inflow site of the pump chamber. This device was tested for VVBP in three pigs (each weighing 52.3 ± 5.1 kg) with hepatic vascular exclusion. Blood was pumped from the femoral and portal veins to the external jugular vein and perfusion was maintained for 6 hours. The hemodynamic state of the animals was assessed by recording heart rate; systolic, mean arterial, and diastolic pressure; as well as central venous pressure. Mean pump flow during the experiment was 1,629.3 ± 372.2 ml/min. After clamping, the inflow line of the pump mean arterial pressure significantly decreased (from 69.5 ± 4.4 to 43.1 ± 3.5 mm Hg), and mean pressure in the femoral vein increased significantly (from 16.1 ± 2.6 to 26.8 ± 5.9 mm Hg), whereas the mean pressure in the internal jugular vein did not significantly change (from 6.0 ± 1.7 to 5.0 ± 2.1 mm Hg). There was no suction by the blood collecting cannula on the vessel wall, and neither bubbles nor air emboli were detected and no operator intervention was needed. In conclusion, the Affinity pump eliminates device related complications due to negative pressure generated at the inlet, and guarantees stable hemodynamics. Its application is simple and safe and minimal operator intervention is needed, making the Affinity pump particularly suited for veno-venous bypass.