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 oncotic pressure values and FVIII values are presented in Table-III.
The effect of the reduction of colloid oncotic pressure, with and without reduction of osmolality, on post-traumatic cerebral edema.
AFP contributes to oncotic pressure in the fetal circulation.
It has been postulated that decreased pulmonary hydrostatic pressure and increased pulmonary oncotic pressure secondary to dehydration or volume depletion may diminish the flux of fluid into the alveoli and interstitium and thus delay or alter the radiographic findings of pneumonia.
oncotic pressure Pressure within a fluid compartment that depends on the concentration of proteins.
The artificial cells were rapidly removed from circulation and they give unfavourable oncotic pressure levels crucial for efficient [O.
The hetastarch component creates oncotic pressure, which would normally be provided by blood proteins, and permits retention of intravascular fluid.
Hypoalbuminemia may cause generalized oedema (Swelling) via a decrease in oncotic pressure.
Fluid movement between the vascular compartment and the interstitial space is regulated by two forces: hydrostastic or hydraulic pressure of the vessel, and oncotic pressure (see Figure 1).
During hemodialysis, blood volume initially decreases within the intravascular compartment leading to an increase in plasma oncotic pressure caused by increase in plasma protein concentration.
Therefore, they should not decrease plasma colloid oncotic pressure (COP) as much as crystalloid solutions and intravascular volume should be better maintained.
Hypoalbuminemia causes changes in oncotic pressure and, consequently, edema, compromising tissue diffusion of oxygen and nutrients, predisposing to hypoxia and cellular death.