Chapter VI. BLOOD COMPONENTS, BLOOD PRODUCTS AND NUTRITIONAL SUPPORT

Most blood collected from donors is processed as follows:

• Blood components (e.g. red blood cell and platelet concentrates; fresh frozen plasma [FFP]; cryoprecipitate) are prepared from asingle donation of blood by simple separation methods such as centrifugation and are transfused without processing

• Blood products (e. g. coagulation factor concentrates; albumin and immunoglobulin solutions) are produced by complex processes using the plasma from many donors as the starting material.

In most circumstances it is preferable to transfuse only the blood component or product required by the patient (component therapy)rather than use whole blood. This is the most effective way of applying donor blood, which is a scarce resource. Besides, it reduces the risk of complications from transfusion of unnecessary components of the blood. Packed red blood cells (red blood cell suspension)Under absolutely sterile conditions some 200-250 ml of plasma are removed from whole blood to be frozen as FFP or to be further processed (preferably packed by centrifuging). Packed red cells obtained in this way must be used promptly. Devoid of white blood cells («leuco-poor») these are associated with reduced incidence of febrile reactions following transfusion

Red blood cell concentrates Virtually all the plasma is removed and replaced by approximately 100 ml of an optimal additive solution, such as SAG-M which contains sodium chloride, adenine, glucose and mannitol. The packed cell volume (PCV) is about 0, 65 l/l, but the viscosity is low as there are no plasma proteins in the additive solution which allows fast administration whenever necessary. Buffy coat-depleted red cell concentrates These are prepared by removal of the buffy coat, which contains most of the leucocytes and platelets. They are useful in preventing febrile reactions in patients with a previous history of reactions and in those likely to receive multiple transfusions (e.g. patients with haematological diseases). Leucocyte-depleted red cell concentrates These are usually produced by filtration and indicated for prevention of alloimmunization to leucocyte antigens (e.g. in aplastic anaemia patients who are potential recipients of allogenic bone marrow transplants).

The source of human whole blood and its components is not unlimited. Due to more and more operations being performed these days and using devices as heart-lung bypass or an artificial kidney that require large amounts of blood, the issue becomes as ever vital. Neither blood obtained from dead people (cadaver's blood) nor blood products have been able to fully meet the needs of transfusiology.

The advances of chemistry, particularly those of enzymology, allow the production of heteroproteins, polysaccharides and synthetic products from raw materials available.

Solutions for parenteral infusion. These are physically homogenous transfusion solutions that have specific properties and act on the body to make up for specific functions of blood. A formulation of different blood products or their use in specific succession can give a complex effect on the body.

Solutions for parenteral infusion must comply with the following requirements:

1. Have physical and chemical properties similar to those of blood plasma.

2. Be able to be fully excreted from the body or fully metabolised by the bodily enzymes.

3. Be unable to sensitise the patient's body on repeated transfusions.

4. Be non-toxic.

5. Be able to withstand the exposure to high temperatures on sterilisation and maintain their physical, chemical, and biological properties for a long period.

Liquid supplements for nutritional support may be classified under the following types:

1) colloid solutions:

• dextran (polyglucin, reopolyglucin);

• gelatin products (poliglucan, gelatinol);

• solutions of polyvinylpirolidon;

2) saline solutions:

• isotonic saline (0, 9%);

• Ringer's solution;

• lactasol;

3) buffer solutions:

• sodium bicarbonate;

• trisamine;

4) solutions of sugar and polyvalent alcohols (glucose, sorbitol, fructose);

5) protein products (protein hydrolysate, amino acid solutions);

6) fatty products - fat emulsions (lipofundin, intralipid).

The solutions for parenteral infusion are indicated for shock, intoxication, parenteral nutrition and acid-base and electrolyte disorders (see Classification).

Classification of solutions for transfusion (based on indications)

I. Anti-shock solutions:

• low molecular dextrans - rheopolyglucin, rheogluman, lomodex;

• moderate molecular dextrans - polyglucin, polypher, macrodex;

• products of gelatin - gelatinol;

• products based on hidroxyethye starch - plasmosteryl, oxyamal, volecam.

II. Detoxicating solutions:

1. Low molecular polyvinylpirobidon - haemodes.

2. Low molecular polyvinic acid - polides.

III. Parenteral nutrition solutions:

1. Amino acid solutions - polyamine, maryamine, friamine.

2. Protein hydrolysates - hydrolysates of casein, amino peptide, aminocrovine, aminosol, hydrolysin.

3. Fatty emulsions - intralipid, lipofundin.

4. Sugars and polyvalent alcohols - glucose, sorbitol, fructose.

IV. Regulators of acid-base balance

1. Saline solutions - normal saline, ringer's solution, lactasol, sodium bicarbonate solutions, trisamine solutions.

V. Oxygen transferring solutions

ANTISHOCK SOLUTIONS

High molecular solutions are able to increase the circulating blood volume and therefore restore normal blood pressure. They can also stay in the blood stream over a long period and draw fluid from the intercellular space. These properties are important in shock. Low molecular blood products enhance capillary perfusion, have a shorter T_1/2, and are eliminated from the body by the kidneys. These properties are used in the management of capillary perfusion insufficiency, dehydration, and detoxication, in which case toxins are rapidly eliminated through the kidneys.

Polyglucin. This is a colloid solution of the fractions of dextran (polyanhydroglucose), - a glucose polymer, produced by the action of certain bacteria on polysaccharides, of moderate molecular weight (MW - 6, 0000±1, 0000). This makes it similar to plasma albumin which maintains normal osmotic pressure in human blood. The product contains dextran 6% in normal saline, with pH being within the range of 4, 5-6, 5. It is stored in sterile 400 ml bottles at -10°...+ 20 °C for 5 years. After thawing therapeutic effects of the product are restored.

Polyglucin elevates and maintains circulating blood volume by attracting fluid from the intercellular space into the bloodstream through its colloid properties. Following infusion of polyglucan an increase in blood plasma volume exceeds the volume of the solution infused. The product circulates in the blood for 3-4 days (T₁/₂ 24 hours).

Circulatory characteristics of polyglucin surpass those of other products. Owing to its osmotic properties polyglucin restores arterial and venous blood pressures and improves blood circulation. Polyglucin contains up to 20% of low molecular fractions of dextran, which is able to stimulate diuresis and thus contributes to elimination of toxic products from the body. Indications for the use of polyglucin are as follows:

1. Shock (traumatic, surgical in severe burns).

2. Acute haemorrhage.

3. Acute circulatory failure resulting from severe intoxication (e.g. peritonitis, sepsis, intestinal obstruction).

4. Circulatory failure (for exchange blood transfusion).

This product is contraindicated for head injury, increased intracranial pressure or intractable internal bleeding.

Stat dose (given once) of the product usually ranges from 400-1, 200 ml; it can, however, if necessary, be increased to as much as 2, 000 ml. Polyglucan is given intravenously (IV) in drops or as a bolus depending on the patient's condition. In emergency, it is initially given as a bolus, and subsequently, i.e. after the blood pressure has increased, the infusion is continued in drops at a rate of 60-70 drops/minute.

Rheopolyglucin. This is 10% low molecular (MW-35, 000) dextran in normal saline. Rheopolyglucin is able to raise the blood circulating volume, each 20 ml of the solution bind an extra 10-15 ml of water from the interstitial fluid. Counteracting aggregation of red blood cells (RBCs) the product inhibits stasis, reduces blood viscosity and increases blood flow. It therefore improves rheologic properties of blood and microcirculation. Thanks to its diuretic potency rheopolyglucan is preferably used in intoxication. The product is eliminated from the body within 2-3 days, but it is mostly excreted through the urine within the first 24 hours. Indications for use are similar to those of other circulatory blood solutions. However, rheopolyglucan can also be used for prevention and treatment of thrombosis, post-transfusion complications as well as prevention of acute renal failure. The average dose of the product is 500-750 ml. It is contraindicated in chronic renal failure.

Gelatinol 8%. This is partially hydrolysed gelatin in normal saline. MW of the product is 20, 000. Owing to its osmotic properties gelatinol increases blood circulating volume. Due to its rheologic effects it improves blood viscosity hence microcirculation. The product lacks nutritional value and is eliminated within a day via the kidneys, and only 20% of gelatinol may be found in the blood in 2 hours after the infusion. It may be given IV, intra-arterially, in drops or as a bolus. Gelatinol is used for artificial blood circulation. The total dose is 2, 000 ml. Acute or chronic nephritis is a relative contraindication for the use of the product.

Emergent transfusion therapy (e.g. in shock, acute haemorrhage, acute circulatory insufficiency) is to be initiated with the solutions that can rapidly restore circulating blood volume. The use of donor blood implies the delay in transfusion as it takes about 20-30 minutes to perform blood typing (ABO grouping and Rh typing, compatibility testing). In its ability to restore circulating blood volume donor blood is not superior to colloid plasma products. Moreover, in shock and severe deficit in circulating blood volume, donor's blood transfusion may contribute to impairment of microcirculation that results from blood hyperviscosity, sloughing blood cells and microthrombosis. Thus in shock and haemorrhage, transfusion therapy should be started with infusion of antishock products - polyglucin or rheopolyglucin.

Chemically, plasmosteryl, volex (as well as Russian made products - volecam, oxyamal) are related to glycogen. These are solutions of hydroxyethye starch, which is broken down by amylase in the blood. They have osmotic properties and potent circulatory effect.

⇐ Предыдущая22232425262728293031Следующая ⇒

Поделиться: