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Demands to blood substitutes
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Demands to blood substitutes

Isotonicity. Osmotic pressure of blood substitutes should be equal to Posm of plasma. 0,9% solution of NaCl is the simplest blood substitute.

Balanced content of inorganic salts.

Isooncoticity. Big molecules are slowly excreted from the bloodstream, it helps extended refresh of volume of circulating blood (VCB). This is reopolyglukin, haemodesis, polydesis.

pH should be equal to the pH of blood plasma.

Sterility.

It should be non toxic.

Classification of blood substitutes

Group 1 – hemodynamical:

Low molecular dextranes – reopolyglukin;

Medium molecular dextranes – polyglukin;

Gelatin substances – gelatinol.

Group 2 – disintoxicational:

Low molecular polyvinylpyrolidon – heamodesis;

Low molecular polyvinyl alcohol – polydesis.

Group 3 – preparations for parenteral nourishment:

Protein hydrolysates – casein hydrolysate,

Aminopeptide, aminokrovin, aminosol, hydrolysin;

Solutions of amino acids – polyamine, maryamin, freeamin etc;

Fatty emulsions – intralipid, lipofundin;

Sugars and polybasic alcohols – glucose, sorbitol, fructose.

Group 4 – regulators of fluid-electrolyte and acid-base balance: saline solutions – isotonic solution of sodium chloride, Ringer’s solution, lactosol, solution of sodium hydrocarbonate, trisamin solution, etc.

Functional system, which provides constancy of the osmotic pressure.

Osmotic pressure is an important physiological constant. Any deviation of osmotic pressure from normal will lead to redistribution of water between cell and intercellular medium.

For maintenance of the osmotic pressure on the same level in the organism there is a functional system, which consists of external and internal part. In basis of external part there are behavioral responses, which are responsible for normalizing of osmotic pressure. If there is increase in osmotic pressure, human feels thirsty and drinks water. If there is decrease in osmotic pressure, human will feel to eat something salty. In basis of internal part there are local mechanisms of reflexes. Local mechanisms are the processes, which occur in blood itself. If decrease of osmotic pressure, excess water is connecting to the low molecular proteins, formed blood cells and Posm increases. If increase of osmotic pressure, excess electrolytes salts is absorbed by formed blood cells and transported to organs (K+, Ca2+ - to muscles, Ca2+, PO43- - to bones, Na+, Fe2+ - to the liver, Na+, Cu2+ - to the spleen, Na+, Ca2+, Zn2+ - to the pancreas) and Posm decreases.

These mechanisms are working during few hours and if Posm will not go to normal, local mechanisms of reflexes will start working.

There are 3 reflexes for the maintenance of Posm:

osmoregulative;

volumeregulative;

Na-uretive.



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