Viscoelasticity and thixotropy of diabetic blood measured at low shear rate

Abstract

This study has compared blood adjusted to 41% hematocrit from 10 insulin-requiring diabetic and 10 nondiabetic subjects matched for age and sex. The relationship between increased low shear rate viscosity in diabetes and blood’s viscoelastic and thixotropic behavior was examined. Increased viscosity in the shear rate range from 0.1 to 1 inverse seconds was again demonstrated. Time-based studies carried out at .024 inverse seconds shear rate with a shearing duration of 20, 60, and 200 seconds showed a distinctly different pattern in diabetes; shear stress developed more rapidly and then fell to a lower level than for nondiabetic blood. The overall response demonstrated that disparities between diabetic and nondiabetic blood were a function of both shearing duration and the time between blood mixing and the initiation of flow. The 20 second patterns were used to estimate the elastic moduli of onset and relaxation. Both moduli were found to be mildly increased in diabetes. Studies in which shearing was repeated after 20 or 50 second nonshearing periods were carried out at 0.27 and 0.66 inverse second shear rates. During the first shearing period the thixotropic component of diabetic blood’s shear stress onset was far more striking than that of nondiabetic blood. During the second shearing period thixotropic behavior and shear stress were both reduced. The difference was particularly noticeable when the shear rate was higher and the duration of flow longer. The observed viscosity of diabetic blood in the shear rate range between 0.1 and 1 inverse seconds is found to be strongly influenced by the length of time from onset of flow. This is due to a substantial increase in the thixotropy of diabetic blood combined with a marginal increase in its elastic resistance. The thixotropic work required to initiate low shear rate flow of diabetic blood is estimated to be more than 30% greater than that for nondiabetic blood.