Where does plasma colloid osmotic pressure mainly come from

The plasma colloid osmotic pressure is mainly produced by proteins in the plasma, among which albumin contributes the most, accounting for about 75% -80%, while globulin and fibrinogen account for 15% -20% and 5%, respectively. The factors that affect osmotic pressure include protein concentration, molecular size, and charge characteristics.

1. Albumin dominance:

Albumin is the protein with the highest content in plasma, with a small molecular weight and negative charge, which can effectively maintain water balance inside and outside blood vessels. When liver synthesis is insufficient or lost due to kidney disease, colloid osmotic pressure significantly decreases, which may cause tissue edema.

2. Globulin assistance:

alpha, beta, and gamma globulin participate in osmotic pressure regulation through synergistic effects. Although immunoglobulin has a relatively large molecular weight, it plays a supplementary role in maintaining osmotic pressure in the short term when its concentration increases during inflammatory reactions.

3. Function of fibrinogen:

As a coagulation factor, fibrinogen has a low concentration in plasma, but its macromolecular properties still contribute about 5% of osmotic pressure. Elevated levels during trauma or infection may temporarily affect blood osmotic balance.

4. Charge effect: The negative charge on the surface of protein molecules can attract cations to form a hydration layer, enhancing the osmotic pressure effect. Albumin can carry 18 negative charges per molecule, making it the most effective substance for maintaining osmotic pressure.

5. Pathological effects:

Decreased albumin synthesis in patients with cirrhosis and protein loss in patients with nephrotic syndrome can both lead to a decrease in colloid osmotic pressure. Monitoring serum protein electrophoresis helps evaluate the risk of osmotic pressure abnormalities. Maintaining normal plasma colloid osmotic pressure requires attention to protein metabolism balance. It is recommended to consume 1.2-1.5 grams/kg of high-quality protein per day, such as fish, egg whites, and soy products. Moderate aerobic exercise can promote liver protein synthesis function and prevent lower limb edema by avoiding prolonged standing. Patients with abnormal liver function or chronic kidney disease should regularly test their serum total protein and albumin levels, and if necessary, undergo nutritional intervention or medication treatment under the guidance of a doctor.