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Determination of Reynolds Shear Stress Level for Hemolysis

Jhun, Choon-Sik*; Stauffer, Megan A.*; Reibson, John D.*; Yeager, Eric E.*; Newswanger, Raymond K.*; Taylor, Joshua O.; Manning, Keefe B.; Weiss, William J.*†; Rosenberg, Gerson*†

doi: 10.1097/MAT.0000000000000615
Biomedical Engineering

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:

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