Repetitive Supra‐Physiological Shear Stress Impairs Red Blood Cell Deformability and Induces Hemolysis

Abstract

The supra-physiological shear stress that blood is exposed to while traversing mechanical circulatory assist devices affects the physical properties of red blood cells (RBCs), impairs RBC deformability, and may induce hemolysis. Previous studies exploring RBC damage following exposure to supra-physiological shear stress have employed durations exceeding clinical instrumentation, thus we explored changes in RBC deformability following exposure to shear stress below the reported "hemolytic threshold" using shear exposure durations per minute (i.e., duty-cycles) reflective of that employed by circulatory assist devices. Blood collected from 20 male donors, aged 18-38 years, was suspended in a viscous medium and exposed to an intermittent shear stress protocol of 1 s at 100 Pa, every 60 s for 60 duty-cycles. During the remaining 59 s/min, the cells were left at stasis until the subsequent duty-cycle commenced. At discrete time points (15/30/45/60 duty-cycles), an ektacytometer measured RBC deformability immediately after shear exposure at 100 Pa. Plasma-free hemoglobin, a measurement of hemolysis, was quantified via spectrophotometry. Supra-physiological shear stress impaired RBC properties, as indicated by: (1) decreased maximal elongation of RBCs at infinite shear stress following 15 duty-cycles (P <0.05); (2) increased real-time RBC deformability during application of the supra-physiological shear stress protocol (100 Pa) following exposure to 1 duty-cycle (F (1.891, 32.15) = 12.21, P = 0.0001); and (3) increased plasma-free hemoglobin following 60 duty-cycles (P < 0.01). The present study indicates that exposure of RBCs to short-term, repeated supra-physiological shear stress, impairs RBC deformability, with the extent of impairment exacerbated with each duty-cycle, and ultimately precipitates hemolysis.

Speed Modulation of the HeartWare HVAD to Assess In Vitro Hemocompatibility of Pulsatile and Continuous Flow Regimes in a Rotary Blood Pump

“…A promising biomarker for hemocompatibility is RBC deformability given that impairments have been observed prior to overt hemolysis following exposure to supra‐physiological shear stress . The current study observed a paradoxical “improvement” in RBC deformability during continuous exposure to the HeartWare HVAD (Table ; P < 0.05); however, similar findings have been suggested to occur secondary to a “filtering” effect of rigid and fragile cells due to hemolysis .…”

“…A promising biomarker for hemocompatibility is RBC deformability given that impairments have been observed prior to overt hemolysis following exposure to supra-physiological shear stress (6).…”

Oxidative Stress Increases Erythrocyte Sensitivity to Shear‐Mediated Damage

“…Given impairments in RBC deformability lead to detrimental functional implications, including the diminished regulation of microcirculatory blood flow and the precipitation of complete cell destruction (8,16), an index of RBC susceptibility to mechanical damage was expressed by calculating the differences in SS 1/2 :EI max relative to control measures (prior to shearing), as a percentage of the control value (22,24):…”

“…In the present study, RBC from 15 healthy donors were washed and incubated for 60 min at 378C with 50 mM phenazine methosulfate (PMS; an agent that generates superoxide within RBC). Incubated RBC and negative controls were assessed for their deformability and susceptibility to mechanical damage (using ektacytometry) prior to the application of shear stress, and also following exposure to 25 different shear conditions of varied magnitudes (shear stress 1, 4, 16, 32, 64 Pa) and durations (1,4,16, 32, 64 s). The salient findings demonstrate that incubation with PMS impaired important indices of RBC deformability indicating altered cell mechanics by $19% in all conditions (pre-and postexposure to shear stress).…”

A Review of Design Considerations for Hemocompatibility within Microfluidic Systems

“…110 Red blood cell damage, in the form of hemolysis, can occur under supraphysiological shear conditions dependent on shear rate and exposure time, 111,112 while repetitive exposure to supraphysiological shear stress can also impair red blood cell deformability. 113 Hemodynamic effects exerted by red blood cells, such as margination 114 and red cell aggregation, or Rouleaux formation, 115 have been shown to scale in proportion to shear.…”