Effective circulating volume

Effective Circulating Volume (ECV):

ECV is the volume of arterial blood (vascular extracellular fluid) effectively perfusing tissue. ECV is dynamic and not a measurable, distinct compartment. ECV is about 0.7 L in a 70 kg individual. This concept is useful for discussion of cardiovascular and renal physiology.

Though ECV normally varies with extracellular fluid, it is uncoupled in diseases, such as congestive heart failure (CHF) or hepatic cirrhosis. Here decreased ECV may lead to volume-depletion responses and edema.

Decreased ECV can stimulate renin secretion or stimulate a sympatheic nervous system response or prostaglandin release (all of which help mediate renal blood flow and glomerular filtration rate among other things).

Reference: John Bullock, Michael B. Wang, Joseph Boyle. NMS Physiology. 4th ed., Lippincott Williams & Wilkins, 2001. pp 337-339.