Blood substitutes employment

Medical appHcations of PFC emulsions for organ perfusion and intravenous uses have received much attention in recent years. The first commercial blood substitute (Fluosol DA 20%, trademark of the Green Cross Corp.) employed perfluorodecalin, and improved, second generation products based on this PFC, or perfluorooctylbromide, are now under development (20,21). The relatively high oxygen dissolving capabiHty of PFCs undedies these appHcations (see Blood, artificial). 

Addition of a hydroxyl group to the aromatic ring of ephedrine as well as changing the substitution on nitrogen leads to a compound whose main activity is to raise blood pressure. Thus, lormation of the Shiff base of the m-hydroxy analog of 30 with bcnzylamine (34), followed by catalytic reduction, yields metar- uiiinol (35). When optically active hydroxyketone is employed in... 

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. 

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. 

The most common method employs the substitution of all pyrimidine nucleotides by their 2, -NH2- or 2 -F-analogs [31]. These confer increased stability to the RNA, because most ribonucleases need the 2 -OH for cleaving RNA. Substitution of only the pyrimidine nucleotides increases the half-life of RNA from seconds to days [28]. Such -modified RNAs are suitable for the detection of analytes in biological samples like blood, serum, or urine. 

Triphenylthiopyrylium salts have been employed as efficient electron transfer photosensitizers to promote the [4+2] cycloaddition between thiobenzophenone and substituted styrenes. A radical cation derived from the thiobenzophenone is involved in the formation of separable diastereoisomeric mixtures of 1,3,4-trisubstituted isothiochromans <2007OL3587>. Interest has been maintained in the photosensitizing properties of thiopyrylium salts for blood disinfection <2007BMCL4406>. Several new thioxanthylium salts have been reported <2007JOC2647, 2007JOC2690>. 

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. 

In Heu of administering a post-accident test, employers may substitute a test administered by on-site police or public safety ofEcials imder separate authority. The employer is allowed to substitute a blood or breath alcohol test and a urine drug test performed by such local ofEcials, using procedures required by their jurisdictions. This may be particidarly useful if that test can be administered before the employer can get to the scene. The employer must obtain a copy of the test results. 

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