Material Effects in Shear-Induced Hemolysis

Abstract

A rotating-disk apparatus for shearing blood was employed to compare 22 materials for their tendency to cause hemolysis during standardized low-stress (130 dynes/cm2 maximum) laminar flow conditions. Rigid plastics, hydrogels, and carbons were among the materials tested. Time-independent ranking of the materials was possible for 75% of the data; these rankings correlated linearly (for polymers) with the critical surface tension gammac over the range 20--46 dyne/cm, with low gammac being associated with low hemolysis. Surface morphology was also found to influence hemolysis. Roughness in the 1--15 micron range had a distinct effect on hemolysis kinetics for polyethylene surfaces. This suggest that failure to find time-independence in 25% of the material rankings can be attributed to inadequate control of the roughness variable. It also emphasizes the importance of surface morphology, as well as surface chemistry, as a biocompatibility parameter.

Red Blood Cell Damage from Extracorporeal Circulation in Hemodialysis

“…Surface roughness and surface chemistry influence hemolysis and may even dominate in capillary flow, especially at shear stress below the critical limit of $150 Pa. Erthroyctes attach to surfaces and develop tethers if exposed to shear stress above 0.2 Pa (36). Hemolysis correlates with the critical surface energy with the exception of PTFE (Teflon) which, although having a low critical surface energy, causes the most hemolysis (37). The surface chemistry depends not only on the bulk composition but also on the production steps.…”

“…The catheter material may have contributed to the problems in all cases mentioned above because PTFE is known to be hemolytic and FEP is a copolymer of PTFE (37). At least one type peripheral catheter [Deseret, Deseret Pharmaceuticals (now BD Medical), Sandy, UT, USA] was made from FEP (fluorinated ethylene propylene).…”

A dual mechanism for low‐stress hemolysis in laminar blood flow

“…To this end, correlations of hemolysis with material chemical parameters (e.g., Monroe et al, 1980;Offeman and Williams, 1979a) are of practical utility. Engineering design requires also an understanding of such factors as fluid shear stress (Leverett et al, 1972) and shear rate (Shapiro and Williams, I%%), surface roughness and device edges and corners (Monroe et al, 1981), and other boundary and interface phenomena (e.g., Offeman and Williams, 1979b).…”

“…Experimental evidence indicates that such hemolysis correlates with shear rate rather than with shear stress, even for older stored bloods (Shapiro and Williams, 1970). It is believed to occur at or near the solid synthetic surface (Blackshear, 1972), the strongest evidence being its sensitivity to surface chemistry (Nyilas et al, 1970Bernstein, 1971Lampert and Williams, 1972;Offeman and Williams, 1979a;Monroe et al, 1980) and to surface morphology, especially roughness (Offeman and Williams, 1979a;Wielogorski et a]., 1976;Monroe et al, 1981).…”

“…The kinetics of low-stress hemolysis are rather slow, being highest at the onset of shear and slowing thereafter; numerous plots of plasma hemoglobin concentration vs. time, when various biomaterial surfaces were used for shearing, have been presented by this laboratory. These kinetic hemolysis curve (KHC) kinetics have been correlated, for polymeric surfaces, with the critical surface energy of those plastics (Lampert and Williams, 1972;Offeman and Williams, 1979a). This material effect is evident despite the fact that plasma proteins adsorb onto synthetic surfaces, thereby rendering them less damaging (Bernstein et al, 1966;Nichols and Williams, 1976).…”