Reynolds shear stress (RSS) has served as a metric for the effect of turbulence on hemolysis. Forstrom (1969) and Sallam and Hwang (1984) determined the RSS threshold for hemolysis to be 50,000 and 4,000 dyne/cm2, respectively, using a turbulent jet. Despite the order of magnitude discrepancy, the threshold by Sallam and Hwang has been frequently cited for hemolytic potential in blood pumps. We recreated a Sallam apparatus (SA) to resolve this discrepancy and provide additional data to be used in developing a more accurate hemolysis model. Hemolysis was measured over a large range of Reynolds numbers (Re) (Re = 1,000–80,000). Washed bovine red blood cells (RBCs) were injected into the free jet of phosphate buffered saline, and hemolysis was quantified using a percent hemolysis, H p = h (100 − hematocrit [HCT])/Hb, where h (mg/dl) is free hemoglobin and Hb (mg/dl) is total hemoglobin. Reynolds shear stress was calculated using two-dimensional laser Doppler velocimetry. Reynolds shear stress of ≥30,000 dyne/cm2 corresponding to Re of ≥60,000 appeared to cause hemolysis (p < 0.05). This RSS is an order of magnitude greater than the RSS threshold that Sallam and Hwang suggested, and it is similar to Forstrom’s RSS threshold. This study resolved a long-standing uncertainty regarding the critical values of RSS for hemolysis and may provide a foundation for a more accurate hemolysis model.
From the *Department of Surgery, The Pennsylvania State University, College of Medicine, Hershey, Pennsylvania; and †Department of Bioengineering, The Pennsylvania State University, College of Engineering, University Park, Pennsylvania.
Submitted for consideration October 2016; accepted for publication in revised form May 2017.
Disclosure: The authors have no conflicts of interest to report.
Reprint Requests: Gerson Rosenberg, Department of Surgery, Division of Applied Biomedical Engineering, The Pennsylvania State University, College of Medicine, 500 University Drive, Hershey, PA 17033. Email: firstname.lastname@example.org