Diabetes mellitus: its effect on the flow properties of blood.

In a group of long-standing diabetics low shear blood viscosity was increased compared with matched non-diabetic controls, being highest in patients with vascular and microvascular complications. Plasma viscosity was also elevated in the diabetics. Conclusions about erythrocyte deformability depended critically on the methodology used. With filtration, red cell deformability was impaired in the diabetic, with centrifugation, diabetic cells were more deformable whilst there was no differences between diabetic and normal red cells by the method of viscometry of packed red cells. The effect of poor metabolic control on blood rheology was investigated in patients recovering from diabetic ketoacidosis and in newly diagnosed maturity onset diabetics being treated at the clinic with diet alone. In both groups, the initially high levels of blood viscosity fell toward normal with improved metabolic control. It is concluded that multiple rheological abnormalities are present in diabetics and appear to be influenced by the metabolic state of the patient. The relationships between these complex changes and the development of microangiopathy remain to be elucidated.