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Hyperviscosity syndrome is a group of symptoms triggered by an increase in the viscosity of the blood.Symptoms of high blood viscosity include spontaneous bleeding from mucous membranes, visual disturbances due to retinopathy, and neurologic symptoms ranging from headache and vertigo to seizures and coma.
Blood viscosity is a measure of the resistance of blood to flow. It can also be described as the thickness and stickiness of blood. This biophysical property makes it a critical determinant of friction against the vessel walls, the rate of venous return, the work required for the heart to pump blood, and how much oxygen is transported to tissues and organs.
η(δ) = viscosity of blood in the wall plasma release-cell layering; r = radius of the blood vessel; δ = distance in the plasma release-cell layer; Blood resistance varies depending on blood viscosity and its plugged flow (or sheath flow since they are complementary across the vessel section) size as well, and on the size of the vessels.
A variety of things can affect blood circulation: blood vessel health, blood pressure, thyroid function, hydration, heart health, exercise, and blood viscosity. (More on this in a moment.)
Polycythemia in newborns is defined as hematocrit > 65%. Significant polycythemia can be associated with blood hyperviscosity, or thickening of the blood. Causes of neonatal polycythemia include: Hypoxia: Poor oxygen delivery (hypoxia) in utero resulting in compensatory increased production of red blood cells (erythropoeisis). Hypoxia can be ...
Erythrocyte aggregation is the main determinant of blood viscosity at low shear rate. Rouleaux formation also determines Erythrocyte sedimentation rate which is a non-specific indicator of the presence of disease. [6] Influence of erythrocyte aggregation on in vivo blood flow is still a controversial issue. [7]
An increased number of red blood cells (polycythemia) causes reduced ESR as blood viscosity increases. Hemoglobinopathy such as sickle-cell disease can have low ESR due to an improper shape of red blood cells that impairs stacking.
Erythrocyte deformability is an important determinant of blood viscosity, hence blood flow resistance in the vascular system. [3] It affects blood flow in large blood vessels, due to the increased frictional resistance between fluid laminae under laminar flow conditions.