Final answer:
An increase in hematocrit elevates blood viscosity by increasing the concentration of erythrocytes and reducing the plasma volume, which can lead to complications in the cardiovascular system.
Step-by-step explanation:
An increase in hematocrit can elevate blood viscosity primarily through two mechanisms:
- Concentration of erythrocytes: Hematocrit is the proportion of blood volume occupied by red blood cells (erythrocytes). Conditions like polycythemia lead to a higher concentration of red blood cells, making the blood thicker and more viscous. In polycythemia vera, overproduction of immature erythrocytes occurs, significantly increasing blood viscosity.
- Reduction in plasma volume: When dehydration occurs, the plasma volume decreases. This effectively increases the percentage of red blood cells in the blood (hematocrit), making the blood more viscous. This is a common transient cause of increased blood viscosity.
Blood viscosity affects blood flow and pressure, thereby impacting the cardiovascular system. Excessive blood viscosity can lead to complications such as high blood pressure and increased cardiac workload.