Microcatheter directed blood reperfusion is an endovascular salvage option for acute cerebral artery occlusions. It has not been investigated whether this technique may be associated with hemolysis.Analysis of hemolysis during blood infusion through different microcatheters and infusion rates to assess related risks.Four microcatheters with different inner diameters were perfused with blood samples at three infusion rates. Hemolytic markers including lactate-dehydrogenase (LDH) and haptoglobin were analyzed. Samples before and after blood infusion were compared using Student's t-test. Flow-related degree of hemolysis was analyzed with regression analysis. Resulting shear stress was calculated and correlated with LDH and haptoglobin.Significant increase of LDH and decrease of haptoglobin was found after blood reperfusion through small microcatheters at progressive flow rates (p<0.05). No hemolysis was found with larger diameter microcatheters at all flow rates (p>0.05). Correlation between shear stress, LDH and haptoglobin was r=0.86 and r=0.75, respectively.Progressive hemolysis occurs during blood perfusion of small lumen microcatheters at increasing flow rates. This phenomenon may be related to turbulent flow, exposure time and increased shear stress. Larger microcatheters did not induce hemolysis and may be the preferred choice for stroke reperfusion.