Hemolysis in a laminar flow-through Couette shearing device: an experimental study

Area of Science:

• Biomedical Engineering
• Fluid Mechanics
• Hematology

Background:

• Reducing hemolysis is critical for rotary blood pump safety and efficacy.
• Accurate estimation of hemolysis at elevated shear stresses is needed for device development.
• Hemolytic behavior and thresholds at subcritical shear exposure remain poorly understood.

Purpose of the Study:

• To experimentally determine hemolysis data for various shear stresses and exposure times.
• To provide data for improved hemolysis estimation in blood exposed to elevated shearing.
• To investigate the relationship between shear stress, exposure time, and blood damage.

Main Methods:

• Heparinized porcine blood (40% hematocrit) was subjected to shear stress in a laminar Couette flow.
• Four shear stress levels (24-842 Pa) and two exposure times (54, 873 ms) were tested at 23°C.
• Index of Hemolysis (IH) was calculated by measuring plasma-free hemoglobin.

Main Results:

• Hemolysis increased exponentially with shear stress.
• At short exposure times (<0.5%), IH remained low across all shear stresses.
• At long exposure times (873 ms), IH increased from 0.84% to 3.57% as shear stress rose from 592 Pa to 842 Pa.
• Significant hemolysis was observed above ~600 Pa at 873 ms exposure.

Conclusions:

• Hemolysis is highly dependent on both shear stress magnitude and exposure duration.
• Shear stresses exceeding approximately 600 Pa at prolonged exposure times cause significant blood damage.
• These findings are valuable for designing safer rotary blood pumps with reduced hemolysis.