Rheological parameter alternations in blood may impair oxygen transported to the retina in type II diabetes (NIDDM)

Rheological properties of blood, retinal capillary blood flow velocity and oxygen transport efficiency (TE) were measured and calculated from 21 type II diabetic patients (NIDDM) and 19 normal subjects. The results showed that the diabetes group had increased plasma viscosity and blood viscosities (P < 0.05 or better) at all tested shear rates. For both shear rates (gamma) of 225 sec-1 and 450 sec-1, the diabetes group displayed increased internal viscosity of red cells (Tk) (P < 0.002 and P < 0.001, respectively) but lower values of TE (P < 0.001, both). A lower value of retinal capillary blood flow velocity (P < 0.005) was also noted. Upon further analysis of possible relations between Hct values and Tk of red cells, it was found that Hct values were linearly correlated with Tk for both shear rates of the diabetes group (gamma = 225 sec-1 and gamma = 450 sec-1; R = -0.63 and -0.65, n = 21 and 19, respectively, both P < 0.005); control group (gamma = 225 sec-1 and gamma = 450 sec-1; R = -0.84 and -0.82, respectively, n = 19, both P < 0.001) and all subjects (gamma = 225 sec-1 and gamma = 450 sec-1; R = -0.70 and -0.72, n = 40 and 38, respectively, both P < 0.001). The impaired rheological properties of blood and internal viscosity of red cells may result in both reduced capillary blood flow velocities and less oxygen transported to tissues. This may possibly contribute to the deterioration of retinopathy or microangiopathy in diabetic patients.