Blood Viscosity: Normal Values, Causes of Abnormalities, and Diagnostic Significance

In recent years, the incidence of blood diseases has been constantly increasing, posing significant health risks to individuals. During blood viscosity tests, some individuals may show elevated levels, while others may have lower-than-normal results. There are numerous reasons that can lead to abnormalities in whole blood viscosity. Many people are unaware of the normal range of blood viscosity. Let's delve into understanding what the normal blood viscosity values are!

1. What is the Normal Range of Blood Viscosity?

The normal range of blood viscosity varies depending on the method of measurement. Firstly, we will focus on the capillary method. For adult males, the normal value is 4.25±0.41. For adult females, the normal range is 3.65±0.32. When using the rotational method, the normal values for males and females are 230/s, 4.53±0.46, and 22±0.41 respectively. Therefore, the key to understanding normal blood viscosity values lies in identifying the specific measurement method. Values above the normal range indicate elevated blood viscosity, which often suggests a higher risk of thrombotic diseases.

2. Causes of Low Blood Viscosity

Low blood viscosity can be observed in hemorrhagic diseases such as hemorrhagic stroke, upper gastrointestinal bleeding, nosebleeds, and functional uterine bleeding. These diseases are characterized by a parallel reduction in blood viscosity and red blood cell ratio, resulting from the transfer of water from tissues to the bloodstream following blood loss. Consequently, these conditions are also known as hemorrhagic hypoviscosity syndromes. Additionally, certain diseases like various anemias, uremia, cirrhosis ascites, and acute hepatitis can also manifest as hypoviscosity, but these reductions are unrelated to hemorrhage and are instead associated with chronic consumptive pathological processes. These conditions are classified as non-hemorrhagic hypoviscosity syndromes.

3. Causes of High Blood Viscosity

Elevated blood viscosity is commonly associated with abnormalities in plasma proteins, such as macroglobulinemia, multiple myeloma, and congenital hyperfibrinogenemia. These conditions lead to an abnormal increase in protein content in the plasma, resulting in increased plasma viscosity and subsequently elevated whole blood viscosity. Additionally, an increase in the number of red blood cells, such as in primary or secondary polycythemia, pulmonary heart disease, leukemia, high-altitude environments, and long-term hypoxia, can also contribute to increased blood viscosity.

4. Significance of Blood Viscosity Measurement

Measuring blood viscosity is valuable for differential diagnosis. Some researchers in cerebrovascular diseases have found that patients with ischemic cerebrovascular diseases often have significantly elevated blood viscosity, while patients with hemorrhagic cerebrovascular diseases may have unchanged or even reduced blood viscosity. In acute myocardial infarction, blood viscosity, especially at high shear rates, is significantly elevated, whereas in severe angina pectoris, the increase in blood viscosity is less pronounced. These differences provide important insights for accurate diagnosis and management of these conditions.