140:, a protein that constitutes approximately 80% of the total oncotic pressure exerted by blood plasma on interstitial fluid . The total oncotic pressure of an average capillary is about 28 mmHg with albumin contributing approximately 22 mmHg of this oncotic pressure, despite only representing 50% of all protein in blood plasma at 35-50 g/L. Because blood proteins cannot escape through capillary endothelium, oncotic pressure of capillary beds tends to draw water into the vessels. It is necessary to understand the oncotic pressure as a balance; because the blood proteins reduce interior permeability, less plasma fluid can exit the vessel.
459:. There is some debate concerning the advantages and disadvantages of using biological vs. synthetic colloid solutions. Oncotic pressure values are approximately 290 mOsm per kg of water, which slightly differs from the osmotic pressure of the blood that has values approximating 300 mOsm /L. These colloidal solutions are typically used to remedy low colloid concentration, such as in hypoalbuminemia, but is also suspected to assist in injuries that typically increase fluid loss, such as burns.
20:
29:
444:, can cause edema and decrease in blood volume as fluid is not reabsorbed into the bloodstream. Colloid pressure in these cases can be lost due to a number of different factors, but primarily decreased colloid production or increased loss of colloids through glomerular filtration. This low pressure often correlates with poor surgical outcomes.
23:
Above, we see a representation of fluid flow in the presence of colloids, with the left side representing surrounding tissues and the right representing whole blood. The presence of colloids can increase the flow towards the high concentration of colloids by creating colloid osmotic pressure in an
428:
At the arteriolar end of the capillary, blood pressure starts at about 36 mm Hg and decreases to around 15 mm Hg at the venous end, with oncotic pressure at a stable 25–28 mm Hg. Within the capillary, reabsorption due to this venous pressure difference is estimated to be around 90%
120:
walls, their effect on the osmotic pressure of the capillary interiors will, to some extent, balance out the tendency for fluid to leak out of the capillaries. In other words, the oncotic pressure tends to pull fluid into the capillaries. In conditions where plasma proteins are reduced, e.g. from
32:
In the illustration above, we see how the osmotic pressure changes over the length of the capillary, with oncotic pressure remaining the same. Overall direction of fluid flow in relation to equal bidirectional flow is shown by the orange and black lines,
424:
294:
207:
265:
236:
178:
93:
filter. However, this concept has been strongly criticised and attention has shifted to the impact of the intravascular glycocalyx layer as the major player.
89:
Oncotic pressure strongly affects the physiological function of the circulatory system. It is suspected to have a major effect on the pressure across the
129:), there will be a reduction in oncotic pressure and an increase in filtration across the capillary, resulting in excess fluid buildup in the tissues (
437:
In tissues, physiological disruption can arise with decreased oncotic pressure, which can be determined using blood tests for protein concentration.
592:"Revised Starling equation and the glycocalyx model of transvascular fluid exchange: an improved paradigm for prescribing intravenous fluid therapy"
101:
The word 'oncotic' by definition is termed as 'pertaining to swelling', indicating the effect of oncotic imbalance on the swelling of tissues.
301:
104:
The word itself is derived from onco- and -ic; 'onco-' meaning 'pertaining to mass or tumors' and '-ic', which forms an adjective.
78:, which pushes water and small molecules out of the blood into the interstitial spaces at the arterial end of capillaries, and the
715:
644:
633:"Chapter 18 - Salt-induced inappropriate augmentation of renin–angiotensin–aldosterone system in chronic kidney disease"
429:
that of the filtered fluid, with the extra 10% being returned via lymphatics in order to maintain stable blood volume.
447:
In the clinical setting, there are two types of fluids that are used for intravenous drips: crystalloids and
632:
270:
183:
136:
The large majority of oncotic pressure in capillaries is generated by the presence of high quantities of
795:
Kim, Sunghye; McClave, Stephen A.; Martindale, Robert G.; Miller, Keith R.; Hurt, Ryan T. (2017-11-01).
455:
of mineral salts or other water-soluble molecules. Colloids contain larger insoluble molecules, such as
241:
212:
154:
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Raghunathan K, Murray PT, Beattie WS, Lobo DN, Myburgh J, Sladen R, et al. (November 2014).
8:
964:
90:
83:
79:
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797:"Hypoalbuminemia and Clinical Outcomes: What is the Mechanism behind the Relationship?"
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and elsewhere. The
Starling equation in particular describes filtration in volume/s (
148:
838:
705:
551:"Choice of fluid in acute illness: what should be given? An international consensus"
82:
colloidal osmotic pressure. These interacting factors determine the partitioning of
912:
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452:
45:
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Throughout the body, dissolved compounds have an osmotic pressure. Because large
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732:
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49:
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Measure of pressure exerted by large dissolved molecules in biological fluids
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854:"The Colloid Controversy: Are Colloids Bad and What Are the Options?"
117:
510:"Microvascular fluid exchange and the revised Starling principle"
456:
448:
137:
53:
296:), as well as several descriptive coefficients, as shown below:
28:
858:
The
Veterinary Clinics of North America. Small Animal Practice
419:{\displaystyle \ J_{\mathrm {v} }=L_{\mathrm {p} }S(-\sigma )}
669:
Gounden, Verena; Vashisht, Rishik; Jialal, Ishwarlal (2021),
130:
122:
65:
61:
548:
476:
Moman, Rajat N.; Gupta, Nishant; Varacallo, Matthew (2021),
440:
Decreased colloidal osmotic pressure, most notably seen in
794:
710:. Library Genesis. Philadelphia : Elsevier Saunders.
704:
Guyton, Arthur C.; Hall, John E. (John Edward) (2006).
68:) that causes a pull on fluid back into the capillary.
86:
between the blood plasma and the extravascular space.
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899:
Cartotto, Robert; Greenhalgh, David (October 2016).
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631:Maitra, Sayantan; Dutta, Dibyendu (2020-01-01).
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771:, Treasure Island (FL): StatPearls Publishing,
739:, Treasure Island (FL): StatPearls Publishing,
677:, Treasure Island (FL): StatPearls Publishing,
635:. In Preuss, Harry G.; Bagchi, Debasis (eds.).
484:, Treasure Island (FL): StatPearls Publishing,
143:Oncotic pressure is represented by the symbol
762:
852:Wong, Christine; Koenig, Amie (March 2017).
507:
267:), and interstitial fluid oncotic pressure (
238:), interstitial fluid hydrostatic pressure (
637:Dietary Sugar, Salt and Fat in Human Health
630:
56:, in a blood vessel's plasma (or any other
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730:
703:
812:
763:Prasad, Rohan M.; Tikaria, Richa (2021),
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566:
525:
27:
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590:Woodcock TE, Woodcock TM (March 2012).
432:
957:
901:"Colloids in Acute Burn Resuscitation"
733:"Physiology, Colloid Osmotic Pressure"
731:Darwish, Alex; Lui, Forshing (2021),
209:) to capillary hydrostatic pressure (
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697:
664:
662:
639:. Academic Press. pp. 377–393.
289:{\displaystyle \pi _{\mathrm {i} }}
202:{\displaystyle \pi _{\mathrm {p} }}
71:It has an effect opposing both the
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508:Levick JR, Michel CC (July 2010).
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260:{\displaystyle P_{\mathrm {i} }}
231:{\displaystyle P_{\mathrm {c} }}
180:) by relating oncotic pressure (
173:{\displaystyle J_{\mathrm {v} }}
116:cannot easily cross through the
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24:otherwise state of equilibrium.
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707:Textbook of medical physiology
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596:British Journal of Anaesthesia
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555:British Journal of Anaesthesia
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950:Overview at cvphysiology.com
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870:10.1016/j.cvsm.2016.09.008
814:10.1177/000313481708301123
917:10.1016/j.ccc.2016.06.002
42:colloid osmotic-pressure
514:Cardiovascular Research
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905:Critical Care Clinics
478:"Physiology, Albumin"
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801:The American Surgeon
433:Physiological impact
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451:. Crystalloids are
84:extracellular water
765:"Microalbuminuria"
609:10.1093/bja/aer515
568:10.1093/bja/aeu301
527:10.1093/cvr/cvq062
416:
286:
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228:
199:
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121:being lost in the
35:
26:
807:(11): 1220–1227.
717:978-0-7216-0240-0
671:"Hypoalbuminemia"
646:978-0-12-816918-6
453:aqueous solutions
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149:Starling equation
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46:osmotic pressure
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114:plasma proteins
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50:plasma proteins
48:induced by the
44:, is a type of
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944:External links
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911:(4): 507–523.
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864:(2): 411–421.
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76:blood pressure
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127:proteinuria
108:Description
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965:Physiology
782:2021-12-09
769:StatPearls
750:2021-12-09
737:StatPearls
688:2021-12-09
675:StatPearls
652:2021-12-10
495:2021-12-09
482:StatPearls
463:References
91:glomerular
58:body fluid
52:, notably
925:1557-8232
878:1878-1306
823:1555-9823
400:π
396:−
385:π
378:σ
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276:π
189:π
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