The blood heat exchanger in intra-arterial selective cooling infusion for acute ischemic stroke: A computational fluid-thermodynamics performance, experimental assessment and evaluation on the brain temperature.

Intra-arterial selective cooling infusion with the autologous blood (IA-SCAI) is a promising therapeutic hypothermia induction method for conferring neuroprotection to acute ischemic stroke (AIS) patients. The blood heat exchanger (BHE) plays a crucial role in IA-SCAI's cooling capacity. However, there are no BHEs currently available that are specifically designed for the IA-SCAI, which requires a low blood flow to be compatible with cerebral hemodynamics. In an effort to develop a BHE for AIS patients, a prototype of a commercial BHE, Medtronic MYOtherm XP®, was mathematically modeled; specifically, computational fluid dynamics (CFD) was used to analyze its hemo- and thermo-dynamic characteristics under low blood flow including temperature distribution, velocity field and shear stress. Our numerical model predicted the hemolysis index to be 0.0041%-0.0581% inside the BHE with blood flows rates of 10 ml min-1-50 ml min-1. The in vitro heat transfer experiment showed that the BHE efficiently cooled the simulated blood from the initial 37 °C-5.8 °C within 150 s by using cold water (200 ml·min-1, 0 °C). The cooled simulated blood was able to cool the simulated blood in the middle cerebral artery of an artificial circulating system from 37 °C to 16.8 °C-33.7 °C depending on the blood perfusion rate (10-50 ml/min). A biological heat transfer mathematical model showed that brain tissue could be cooled by 2 °C within the initial 1min of infusion. This study verified the feasibility of using a commercial BHE for IA-SCAI and provided insights into its cooling capacity for therapeutic hypothermia.