Oncotic Pressure

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oncotic pressure

[äŋ′käd·ik ′presh·ər]
(physiology)
Also known as colloidal osmotic pressure.
The osmotic pressure exerted by colloids in a solution.
The pressure exerted by plasma proteins.

Oncotic Pressure

 

the component of osmotic pressure that is contributed by substances of high molecular weight in a solution.

In human blood plasma, oncotic pressure ranges from 3 to 4 kilonewtons per square meter, or from 0.03 to 0.04 atmospheres; this constitutes only about 0.5 percent of the total osmotic pressure. Nevertheless, oncotic pressure plays a major role in the formation of some of the body’s fluids, including the intercellular fluid and capsular urine.

The walls of capillary blood vessels are readily permeable to water and substances of low molecular weight, but not to proteins. The filtration rate of fluid through the capillary wall is determined by the difference between the oncotic pressure, which is contributed by plasma proteins, and the blood’s hydrostatic pressure, which is a function of the heart. The saline solution at the arterial end of the capillary passes into the intercellular space together with nutrients. At the venous end of the capillary the process takes place in the opposite direction, since venous pressure is lower than oncotic pressure, and substances that are eliminated by the cells pass into the blood (see).

The oncotic pressure diminishes in diseases that involve a decrease in the concentration of blood proteins—especially albumins. This pressure decrease may be one of the reasons why fluid accumulates in the intercellular space and causes edema.

IU. V. NATOCHIN

References in periodicals archive ?
The blood samples were obtained at different points, including immediately before the operation and 60 and 120 minutes after the procedure for the determination of blood and plasma viscosity, plasma oncotic pressure, INR, PT, aPTT and fibrinogen.
It was enough to produce oncotic pressure preventing any appearance of pulmonary edema, which could interfere with our data.
11 * CUR = curcumin, 5/6NX = five-sixths nephrectomy, NAC = N-acetylcysteine, BW = body weight, KW= kidney weight, GFR = glomerular filtration rate, SNFF= single-nephron filtration fraction, Kf = ultrafiltration coefficient, CA =afferent protein concentrati on, [pi]A = afferent oncotic pressure.
The mechanism postulated for asymmetrical edema in the affected extremity was the inability to increase lymphatic flow during periods of hypoalbuminemia to levels sufficient to reduce the interstitial oncotic pressure gradient.
It provides the majority of intravascular oncotic pressure and contributes to the regulation of fluid concentrations in tissues.
Colloid oncotic pressure and body water dynamics in septic and injured patients.
Review article: albumin as a drug--biological effects of albumin unrelated to oncotic pressure.
3) The main functions of albumin have been summarized to include maintenance of blood oncotic pressure and pH; binding and transport of physiologically important ligands, including lipids, metal ions, amino acids and other factors; and TEN antioxidant functions.
This is followed by plasma volume contraction, increased capillary permeability and, in severe cases, low plasma oncotic pressures.
In contrast to transudative effusions, which are usually due to disequilibrium of local oncotic and hydrostatic forces, exudative effusions are often due to a variety of inflammatory conditions.
SA is consistently decreased in PE, the patients thus manifesting decreased oncotic pressure resulting in more intravascular fluid entering or remaining in the extravascular space.
Review article: albumin as a drug-biological effects of albumin unrelated to oncotic pressure.