Hemodynamic comparison of two different pediatric aortic cannulas.

Any extracorporeal blood treatment requires an adequate and safe connection to the circulation. For cardiopulmonary bypass procedures, aortic and venous cannulas are utilized. However, the performance of these cannulas is not only dependent on their size (diameter), but also on their complete geometric design. In this paper two aortic cannula designs are evaluated hemodynamically for two different sizes (8, 10 Fr) both with aqueous fluids and with blood. Using the novel concept of equivalent diameter, a new performance parameter, and the theory of dynamic similarity the results obtained with different fluids can be compared. Data points of one cannula can be fitted to a parabolic equation. There is a significant performance difference between the two 8 Fr cannulas. The 10 Fr cannulas differ non-significantly except when water is used. Equivalent diameters obtained with water in the turbulent region are significantly higher than those obtained with fluids that have a higher viscosity (blood and aqueous glycerine mixture). The latter fluids have comparable viscosities and render an equal equivalent diameter. The coefficients of their proper parabolic fit lines can easily be recalculated into each other. This provides a simple method to quickly determine pressure drops in cannulas in the operating room.