For example, when ECF volume is low, the body reduces urinary sodium excretion to a minimum and hopes that more sodium will be ingested. Conversely, when the ECF volume is excessive, the body increases urinary sodium excretion and hopes that the individual will not eat incredible amounts of salt.

What happens when extracellular fluid volume decreases?

ECF volume is related to effective circulating volume. A decrease in ECF (hypovolemia) generally causes a decrease in effective circulating volume, which in turn causes decreased organ perfusion and leads to clinical sequelae.

How does ECF affect blood pressure?

In general, the elevation of extracellular fluid (ECF) increases the preload, which eventually contributes to the generation of hypertension. However, the volume of ECF in hypertension has been reported to be diverse (expanded, normal or reduced), and most results were from small-sized studies.