Biomedical subjects

R D Offeman

Publications and source records attributed to R D Offeman.

3 recordsLinked to original sources

PubMed1979

Material effects in shear-induced hemolysis.

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.

Acrylamides↗

PubMed1979

Observations on shear-induced hemolysis.

New data are reported on chemical and mechanical factors affecting the hemolysis of blood in a rotating-parallel-disk apparatus used in biomaterials studies described elsewhere. The hemolytic potential for a blood is found to correlate with plasma components LDH and total triglycerides existing prior to shear. Antibiotics are shown to suppress hemolysis, unrelated to bacterial action. The kinetics of measured hemoglobin release are analyzed in terms of a red cell population having a distribution of fragilities, sample storage age, and possible hemoglobin adsorption. Blood/gas interfacial effects are examined by varying the gas and the extent of interface, and found to be minimal under normal testing conditions. Several geometric and dynamic parameters are varied to illustrate the complexities of engineering design and scale-up.

Biocompatible Materials↗

PubMed1976

Shear-induced hemolysis: effects of blood chemistry (including aging in storage) and shearing surfaces.

Rotating disks were used to hemolyze blood under low-stress laminar flow conditions. In the first sequence of tests, kinetic hemolysis curves (KHC) were obtained with polyethylene disks for three well-characterized bloods and repeated over a period of four weeks. Each blood had a KHC with different shape, which maintained its characteristics while aging. Correlations were sought between D6000 (percent of complete hemolysis, after 6000 sec of shear) and D0 (measured before shear) by two means of data analysis, in terms of blood chemistry. It was found that uric acid and very-low-density lipoprotein levels were most useful in predicting the characteristic D6000 vs. D0 relation for each blood, and that glucose levels correlated the rate of aging as measured by hemolysis. Other chemical factors are also displayed in terms of their influence on D0. The second series of tests consisted of comparing the KHC for four disk materials using a fourth blood, then repeating with a fifth blood. Hemolytic rankings of the materials were the same with these two blood, although the KHC shapes differed. The rankings were: polyvinyl chloride greater than Silastic approximately equal to polyethylene greater than polyether urethane, with PVC most hemolytic. In another sequence for examining materials effects, five different bloods were used to compare the hemolytic properties of Teflon, nylon, and polyethylene disks. Although the KHC for the three disks bore different relationships to each other with each different blood, extrapolation of data beyond 6000 sec suggests a ranking of Teflon greater than nylon greater than polyethylene.

Biocompatible Materials↗