Hemolysis is one of the most important performance parameters of blood pumps. However, comparative in vitro evaluation of the reported hemolysis effect is difficult owing to the lack of uniformity in the test methods used. Currently, three types of formulas are generally accepted and widely used for the index of hemolysis: the traditionally used index of hemolysis (defined as grams of plasma free hemoglobin released per 100 L of blood pumped); the normalized index of hemolysis (normalized by hematocrit); and the modified index of hemolysis (taking into account not only hematocrit but also hemoglobin). In addition, the tested blood conditions are often not indicated in the reports.

If we limit the acceptable range of hemoglobin in human blood, the normalized index of hemolysis is sufficient. Furthermore, using milligrams as the unit of expression would be easier and reasonable for comparing the less hemolytic blood pumps, such as the centrifugal pumps that are currently available clinically