Blood viscoelasticity

Blood viscoelasticity refers to the property of blood that enables it to deform and flow under applied stress and then return to its original shape once the stress is removed. This characteristic is crucial for the efficient functioning of the circulatory system, allowing blood to flow through vessels of varying diameters and across different pressure gradients. Blood viscoelasticity is determined by several factors, including the composition of the blood, the hematocrit level (the proportion of red blood cells in blood), the presence of various proteins and cells, and the shear rate (the rate at which adjacent layers of fluid move with respect to each other).

Composition and Factors Influencing Blood Viscoelasticity

Blood is a complex fluid composed of plasma, red blood cells (RBCs), white blood cells (WBCs), and platelets. Plasma, the liquid component of blood, contains water, salts, proteins, and other substances. The cellular components, especially RBCs, play a significant role in determining the viscoelastic properties of blood.

• Plasma Viscosity: Plasma's viscosity is influenced by the concentration and types of proteins present, such as albumin, fibrinogen, and globulins. These proteins contribute to the overall viscoelasticity of blood.
• Hematocrit Level: The hematocrit level, or the volume percentage of RBCs in blood, significantly affects blood viscoelasticity. Higher hematocrit levels increase blood viscosity, making it more resistant to flow.
• Cell Deformability: The ability of RBCs to deform as they pass through narrow capillaries is crucial for maintaining low resistance to blood flow. Alterations in cell deformability can affect blood viscoelasticity.
• Aggregation of Red Blood Cells: RBCs can aggregate, forming rouleaux structures, which influence blood's viscoelastic properties. The extent of aggregation is affected by the plasma protein concentration and the shear rate of blood flow.

Measurement of Blood Viscoelasticity

Blood viscoelasticity is measured using rheometers, which apply stress to a blood sample and measure its deformation. These measurements can be performed under steady or oscillatory shear conditions to evaluate both the viscous and elastic properties of blood.

Clinical Significance

Alterations in blood viscoelasticity can indicate or contribute to various pathological conditions. Increased blood viscosity is associated with cardiovascular diseases, such as hypertension and atherosclerosis, as it can lead to increased vascular resistance and impaired blood flow. Conversely, decreased blood viscosity can result in excessive bleeding. Understanding blood viscoelasticity is also important in the development of artificial blood substitutes and in the design of biomedical devices that come into contact with blood.

See Also

• Hemorheology
• Blood viscosity
• Circulatory system