Comparing fluid dynamics of newborn and adult centrifugal pumps in cardiopulmonary bypass procedures

Background

Cardiopulmonary bypass (CPB) plays a crucial role in cardiac surgery, with the pump being a key component affecting both hemolysis and thrombosis. Centrifugal levitating pumps (CP) have demonstrated superiority over roller pumps due to reduced hemolysis, but thrombotic risk remains a concern. Nonetheless, there exists a technological gap for newborn patients, with only two approved centrifugal pumps specifically tailored for their needs. Consequently, pumps originally designed for adults are often employed as substitutes for paediatric patients. However, the mismatch between pump characteristics and paediatric physiology can lead to issues like blood dilution, increased shear stress, and suboptimal performance.

Methods

This study investigates the hemodynamics of an adult CP compared to a downscaled newborn CP featuring a 40% reduction in priming volume. Computational fluid dynamics is used to assess differences in flow characteristics, shear stresses, and stagnation zones, with implications for blood damage and thrombogenicity.

Results and conclusion

The newborn pump features notably shorter exposure times (45% lower than the adult design), reduced peak stress values, and a 20% reduction in the volume of fluid exposed to stress levels exceeding 50 Pa, suggesting a potential decrease in the risk of blood damage. Additionally, its reduced extent of stagnation zones (0.13 ml compared to 0.21 ml) indicates improved washout performance, thus lowering the risk of platelet aggregation and thrombus formation. These findings suggest that using a paediatric pump instead of an adult pump at typical flow rates for newborn patients may reduce the risk of blood damage.