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HANDBOOK OF PHYSIOLOGY 



CIRCULATION 



metabolized, not causing either immediate or delayed 

 tissue damage; h) must not be antigenic. Squire and 

 associates (94) have also indicated that the plasma 

 substitute must remain in the blood stream for an 

 appreciable time, preferably that not more than 25 % 

 be excreted in the urine in the first 24 hours, or that 

 at least 50 % of the amount infused be present in the 

 blood stream for at least 12 hours and preferably for 

 24 hours following infusion. The solution should be 

 fluid at temperatures above zero degrees centigrade. 

 It should withstand sterilizing by autoclaving. It 

 should not be locally or generally to.xic. It should 

 not act as a diuretic and should cause no increase, 

 or only slight increase, in the erythrocyte sedimenta- 

 tion rate. The agent should not produce hemolysis 

 or red cell agglutination. Additional requirements 

 have been listed by Hartman (47). The normal 

 number and function of the formed elements of the 

 blood should be maintained. Rapid accumulation of 

 the plasma expander in organs and tissues, thus 

 possibly interfering with their function, should not 

 occur. Prolonged retention of the plasma substitute in 

 organs or tissues contraindicates its use. The material 

 should be at least partially metabolized in the body. 

 Recent studies have indicated that an additional 

 requirement should be made to the above: namely, 

 that the infusion of reasonable amounts of the plasma 

 volume expander, approaching perhaps one-third 

 of normal blood volume, should not be associated 

 with significant impairment of hemostasis. 



ADVANTAGES OF COLLOIDAL INFUSIONS 

 AS PLASMA SUBSTITUTES 



If ample blood and plasma are available there 

 would seem to be limited use, if any, for plasma 

 substitutes; however, in dealing with emergency 

 situations or casualties in\ol\ing a large population, 

 or in working in remote areas where blood or plasma 

 is not available, plasma expanders may become of 

 extreme importance. Plasma expanders have the 

 advantage that they may be manufactured in un- 

 limited quantities, whereas the supply of blood plasma 

 is always limited. Plasma expanders can be stored 

 for many months, whereas whole blood can be stored 

 for only 3 weeks, and cannot be procured in unlimited 

 quantities. In most instances of shock there is a 

 considerable reserve of oxygen carrying capacity, 

 and the primary objective is restoring the circulatory 

 blood volume (45). This, the plasma expanders are 

 able to do. In addition, a suitable plasma expander, 



which can be autoclaved, is free of the risk of trans- 

 mission of bacterial infection and of viral hepatitis, 

 problems which still exist with regard to blood and 

 plasma. The problems of transfusion reaction and Rh 

 sensitization, which are present with the use of blood, 

 are also avoided. Plasma substitutes may be of 

 value in the treatment of shock due to blood loss 

 when blood is not available and when the blood loss 

 is not excessive They are of value in the treatment 

 of shock due to plasma depletion and in the treatment 

 of hypoproteinemia with edema, and they provide 

 useful physiologic tools for studies of experimental 

 hypervolemia and experimental anemia. 



PROPERTIES OF PLASMA SUBSTITUTES 



Plasma expanders may be classified as follows: 

 a) blood derivatives: albumin, plasma, globin; h) 

 modified proteins: gelatin, oxypolygelatin; c) poly- 

 merized carbohydrates: dextran, levan; and d) 

 plastics: polyvinylpyrrolidone (P\'P). 



Since most of the plasma substitutes are available 

 in varying molecular weights and in several different 

 concentrations, only general statements about their 

 properties can be made. According to Hueper (53) 

 acacia is a polysaccharide composed of arabinose and 

 galactose molecules with various hexoses, pentoses, 

 and uronic acids. Polyvinyl alcohol is a polymerized 

 form of unsaturated \inyl alcohol (CH2=CHOH)n. 

 The molecular size depends on the degree of poly- 

 merization. Pectins are long-chained compounds of 

 galacturonic acid molecules with various additional 

 groups — e.g., galactose, araban, acetic acid, and 

 methyl alcohol. Polyvinylpyrrolidone (97) has the 

 following formula : 



PVP 



"CH.2 



I 

 CHo 



-CH.. 



I 

 CO 



I 

 -CH— CH-:— 



Dextran, according to Squire and associates (94), 

 is a collective name for a series of polyglucoses, having 

 a higli dextrorotation of the order of plus 200°. 

 There are various species of cocci belonging to the 

 genus Leuconostoc; two of these, Leuconostoc vusente- 

 roides and Leuconostoc dtxtraniciim, under suitable 

 conditions may produce dextran by the fermentation 

 of sucrose. Dextran is a polyglucose in which the 

 majority of bonds linking the glucose units are of 

 the alpha i :6 type. Dcxtrans may ha\c a wide variety 



