Plasma colloid osmotic pressure

Plasma colloid osmotic pressure, also known as oncotic pressure, refers to the component of total blood plasma osmotic pressure that is generated by large plasma proteins—primarily albumin—which are unable to cross capillary walls. This force acts to pull water into the circulatory system and opposes hydrostatic forces that push water out into surrounding tissues. The normal range for plasma colloid osmotic pressure in humans is approximately 25–30 mmHg, with albumin accounting for about 80% of this effect despite being only about half the total protein content in plasma. The balance between hydrostatic and oncotic pressures across capillaries determines net movement of fluid according to Starling’s law; disruption can result in pathological states such as edema when oncotic pressure falls due to loss or decreased synthesis of plasma proteins. Plasma colloid osmotic pressure itself is not a molecular target like an enzyme or receptor but rather a physical property arising from collective action of circulating macromolecules—mainly albumin—and thus should not be considered a therapeutic target per se.

Other names

Oncotic pressureColloid osmotic pressure