Colloidal plasma expanders

Alternatively, colloidal plasma expanders (Table 9.3) are used. When administered at appropriate concentrations, they exert an osmotic pressure similar to that of plasma protein, hence vascular volume and blood pressure are maintained. The major disadvantages of colloidal therapy include its relatively high cost, and the risk of prompting a hypersensitivity reaction. Determined elforts to develop blood substitutes were initiated in 1985 by the US military, concerned about the issue of blood supply to future battlefields. 

Apart from colloidal plasma expanders crystalloid (electrolyte) fluids are used in certain clinical conditions. 

Table 9.3. Some colloidal plasma volume expanders currently in therapeutic use. In addition to these, albumin and plasma protein fraction may also be used...

Gum-Saline. Gum is a galactoso—gluconic acid having molecular weight of approximately 1500. First used (16) in kidney perfusion experiments, gum—saline enjoyed great popularity as a plasma expander starting from the end of World War I. The aggregation state of gum depends on concentration, pH, salts, and temperature, and its colloid oncotic pressure and viscosity are quite variable. Conditions were identified (17) under which the viscosity would be the same as that of whole blood. 

Use Pharmaceuticals blood plasma expander cast films adherent to glass, metals, and plastics com-plexing agent detoxification of chemicals such as dyes, iodine, phenol, and poisonous drugs. Tablet-ing, photographic emulsions, cosmetics (hair sprays, shampoos, hand creams, skin lotions), dentifrices, dye-stripping, textile finishes, protective colloid, detergents, adhesives, beer and wine clarification. 

The need for the immediate treatment of hemorrhagic circulatory insufficiency with plasma expanders (i.e., crystalloids or colloids) seems obvious, but no large, well-controUed trials in humans have been conducted that support this practice. To the contrary, there is evidence to suggest that fluid resuscitation beyond minimal levels (i.e., mean... 

TABLE 24—4. Adverse Effects of Plasma Expanders Colloids... 

Dextran is used clinically as a colloid osmotic plasma expander in case of shock and prophylactically in cases of postoperative and post-traumatic tromboembohc conditions. 

Polyvinylpyrrolidone (PVP) was widely used during World War II and the Korean War as a plasma expander. Subsequently, PVP was extensively studied and it was found that this synthetic water-soluble polymer cannot be broken down in the body. Thus it is used today only to a limited extent. Since this substance illustrates the problems encountered in the use of completely synthetic colloids as plasma expanders, a short survey, mainly of historical interest, will be presented. 

Colloidal systems can be divided into lyophilic and lyophobic systems. Lyophilic colloids have a strong affinity with the dispersion medium by which a solvation shell around the particle is formed. This process is called solvation and if the dispersion medium is water it is called hydration. A polysaccharide dissolved in water is an example of a lyophilic colloidal system. The solvation shell is formed by hydrogen bonds between the hydroxyl groups of the polymer molecules and the water molecules. Pharmaceutical examples are solutions of dextran, used as plasma expanders. Micelles are also lyophilic colloids. Example of such a system is the aqueous cholecalciferol oral mixture (Table 18.15). In these preparations, a lipophilic fluid is dissolved in an aqueous medium by incorporating it in micelles. Because this type of colloids falls apart on dilution to concentrations below the CMC, they are also known as association colloids. Lyophobic colloids have no affinity with the dispersion medium. Thus, in this type of colloids no solvation shell is formed around the particles. An example of lyophobic particles are colloidal gold particles (with a diameter of 1 nm - 1 pm) dispersed in water. There are no... 

Uses Solubilizer, stabilizer, protective colloid, suspending agent, dispersant, binder, film-former for parenteral applies., antibiotics, antiseptics, steroid hormones, vitamins bioadhesive blood plasma expander detoxicant reduces irritation at in], site clarifier for beer, wine, vinegar tableting adjuvant for vitamins, minerals, flavor cones., nonnutritive sweeteners stabilizer, bodying agent, dispersant in foods Features Pyrogen-free... 

Human albumin is a colloid used as a plasma volume expander and is not a source of nutrition. Albumin should be administered separately from PN because it may be incompatible and... 

To eliminate the threat of shock, replenishment of the circulation is essential. With moderate loss of blood, administration of a plasma volume expander may be sufficient Blood plasma consists basically of water, electrolytes, and plasma proteins. However, a plasma substitute need not contain plasma proteins. These can be suitably replaced with macromolecules ( colloids ) that like plasma proteins, (1) do not readily leave the circulation and are poorly filtrable in the renal glomerulus and (2) bind water along with its solutes due to their colloid osmotic properties. In this manner, they will maintain circulatory filling pressure for many hours. On the other hand, volume substitution is only transiently needed and therefore complete elimination of these colloids from the body is clearly desirable. 

Three colloids are currently employed as plasma volume expanders— the two polysaccharides, dextran and hydroxyethyl starch, as well as the polypeptide, gelatin. 

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