Hyperviscosity syndrome refers to the clinical sequelae of increased blood viscosity. The complications most commonly associated with this syndrome include mucous membrane bleeding, retinopathy, and neurologic symptoms.
Viscosity is the property of fluid to resist flow.
As serum proteins increase, the blood becomes more viscous, leading to the clinical symptoms of hyperviscosity syndrome. The normal relative serum viscosity ranges from 1.4-1.8 units. Symptoms usually are not seen at viscosities of less than 4 units, and the hyperviscosity syndrome typically requires a viscosity greater than 5 units. Confusion and mental status changes result from the increased viscosity of the blood and decreased cerebral blood flow. This sludging leads to segmental dilatation of retinal veins and retinal hemorrhages.