Plasma Volume and Vascular Capacitance

Plasma volume and vascular capacitance are fundamental physiological parameters that govern systemic hemodynamics and cardiac preload. Plasma volume represents the total liquid volume within the intravascular compartment, which is tightly regulated by the kidneys through the renin-angiotensin-aldosterone system (RAAS) and the action of antidiuretic hormone (ADH) (StatPearls, Physiology, Blood Volume, 2023). Vascular capacitance refers to the volume-pressure relationship of the vasculature, primarily determined by the venous system, which contains approximately 70% of total blood volume (NIH, Vascular Capacitance, 2022). In cardiovascular diseases such as heart failure, dysregulation of these parameters leads to fluid overload and increased venous pressure, contributing to edema and pulmonary congestion (PubMed, Pathophysiology of Heart Failure, 2021). Therapeutic strategies involve the use of diuretics to decrease plasma volume and vasodilators, specifically venodilators like nitroglycerin, to increase vascular capacitance, thereby reducing the workload on the heart (Merck Manual, Treatment of Heart Failure, 2023). Because these represent systemic physiological states rather than individual proteins or receptors, they are considered physiological targets or clinical endpoints rather than discrete molecular therapeutic targets.

Other names

Blood volumeIntravascular volumeVenous capacitanceVascular toneEffective circulating volume

Drugs modulate these parameters by promoting renal sodium and water excretion (diuretics) to reduce plasma volume, or by inducing smooth muscle relaxation in the venous system (venodilators) to increase vascular capacitance and reduce cardiac preload.