Plasma substitutes Dextran

Dextran is a polyglucose biopolymer characterized by preponderance of a-1,6 linkage, and generally produced by enzymes from certain strains of Leuconostoc or Streptococcus. While formerly its principal utility was as a blood plasma substitute, dextran is also used in various fields such as pharmaceutical, photographic,... 

A number of other polysaccharides, such as glycogen, dextran, chitin, etc., possess interesting structures for chemical modification [103,104]. Dextran has been used as a blood plasma substitute. Although it can be converted to films and fibers, chitin s relatively small resource restricts its commercialization. 

Dextrans are particularly useful and are employed as a plasma substitute. A concentration of about 6% dextran (50,000-100,000 relative molecular weight) has equivalent viscosity and colloid-osmotic properties to blood plasma. Dextran can also be used as non-irritant absorbent wound dressings, an application also suited to alginate gels. 

Other important examples are blood and blood products, which are collected and processed in sterile containers, and plasma substitutes, for example dextrans and degraded gelatin. Dextrans, glucose polymers consisting essentially of (1 - 6) a-links, are produced as a result of the biochemical activities of certain bacteria of the genus Leuconostoc, e.g. L. mesenteroides (see Chapter 25). 

Dextrans are produced commercially for use as plasma substitutes (plasma expanders) which can be administered by intravenous injection to maintain or restore the blood volume. They can be used in applications to ulcers or bum wounds where they form a hydrophilic layer which absorbs fluid exudates. 

In addition to murein, bacterial polysaccharides include dextrans—glucose polymers that are mostly al 6-linked and al 3-branched. In water, dextrans form viscous slimes or gels that are used for chromatographic separation of macromolecules after chemical treatment (see p.78). Dextrans are also used as components of blood plasma substitutes (plasma expanders) and foodstuffs. 

On the positive side, dextran itself has been refined and employed as a therapeutic agent in restoring blood volume for mass casualties. Natural dextrans have very high molecular weight (on the order of 10 -10 Da) and are found to be unsuitable as a blood-plasma substitute. Lower molecular weight (about 10 Da) dextran is suitable and often referred to as clinical dextran. 

Many pioneer structural investigations were carried out in other groups of polysaccharides, notably on inulin, on the xylan from esparto, on the mannan from yeast and on a series of bacterial polysaccharides amongst the latter were included somatic and lipoid-bound polysaccharides from M. tuberculosis. Noteworthy also was the work on the dextran produced by strains of Leuconostoc, which is showing grqat promise as a blood plasma substitute. 

The most important adverse effect results from the antigenicity of dextrans, which may lead to an anaphylactoid reaction. Dextran antibodies can be intercepted without an immune response by injection of small dextran molecules (MW 1000), thus obviating any incompatibility reaction to subsequent infusion of the dextran plasma substitute solution. 

For use as a blood-plasma substitute, the dextran should have a molecular weight in the range of 50,000 to 100,000. This criterion has occasioned a concerted effort to produce dextrans in the correct range. Partial, acid hydrolysis of native dextran followed by fractionation with various solvents, or enzymic production of dextran of low molecular weight are methods which have been used. In addition, ultrasonics has been suggested as a means of depolymerizating native dextran to the correct size for clinical use. Introduction of alternative acceptors into the reaction mixture for enzymic synthesis has also been employed for this purpose it is described in an earlier Section of this Chapter. 

Dextran 70, so-called because its molecules have an average weight of 70 kDa, is used as a plasma substitute, as is dextran 40. Dextran 40 has been used to improve blood flow in ischemic limbs. Dextran 40 and dextran 70 have been used to prevent deep venous thrombosis. Dextran 1 is used as a desensitizer to prevent allergic reactions to dextrans of larger molecular weight. After reproductive surgery 32% dextran 70 is sometimes administered... 

Dextran (O Scheme 5) solutions have been used as a plasma volume expander since 1947 owing to their non-immunogenic and well-tolerated nature as plasma substitutes [10]. Furthermore, since dextran suppresses erythrocyte aggregation and reduces blood viscosity, it has... 

Certain fractions of partially hydrolysed dextran are used as plasma substitutes or expanders. Certain strains of Leuconostoc meserentoides are cultivated to synthesise dextran (XIII), which is a polymer of anhydroglucose, linked through a-1,6 glucosidic linkages. The chains are branched on the average, one branch occurs for every 10-12 glucose residues. The intrinsic viscosity [ij is related to Mby the relationship... 

Desmopressin - antidiuretic hormone analogue, diabetes insipidus Dexamfetamine - CNS stimulant to treat ADHD Dextran - plasma substitute fluid replacement Diamorphine - opioid analgesic... 

Dextran Used as isotonic plasma substitutes to regenerate the volume of body fluids after great loss of blood... 

The pathomechanism of HES-induced anaphylactoid reactions is unknown. Since HES has been in general clinical use for a comparatively short time, only a few data are available for critical evaluation of the triggering mechanisms of adverse reactions. From the physicochemical properties of HES a few possible mechanisms may, however, be visualized. Comparing the occurrence in humans of preformed antibodies reactive with plasma substitutes, it is evident that both titers and frequency are highest for gelatin, intermediate for dextran, and lowest for HES. In this connection, it is interesting to note that upon rapid infusion of HES into hu-... 

Hedin H, Richter W, Messmer K, Renck H, Ljungstrom KG, Laubenthal H (1981 b) Incidence, pathomechanism and prevention of dextran induced anaphylactoid/anaphylactic reactions in man. Dev Biol Stand 48 179-189 Hehre EJ, Neill JM (1946) Formation of serologically reactive dextrans by streptococci from subacute bacterial endocarditis. J Exp Med 83 147-162 Hehre EJ, Sugg JY (1950) Serological reactivity of dextran plasma substitute. Fed Proc 9 383... 

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