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COLLOIDSDr. Abhijit S. Nair Consultant AnesthesiologistHyderabad

Colloids A high molecular weight solution that largely remains in the intravascular compartment, thereby generating an oncotic pressure

ClassificationNatural ALBUMINArtificial Gelatins, Dextrans,Starches

ALBUMINConsists of a single polypeptide chain of 585 amino acids with a molecular weight of 69,000 DaltonMonodisperse colloid i.e. all particles have same molecular weight

5%: ISO-ONCOTIC80% volume expansion25%: HYPERONCOTIC 200-400% volume expansion

IndicationsBurnsClinically significant hypo-albuminemiaParacentesisLiver transplantHRS in CLDSBP? Acute lung injury

AdvantagesNaturalHigher degree of volume expansionAntioxidant and scavenging effects

DisadvantagesExpensiveVolume overload

DextranBranched polysaccharide moleculeproduced by synthesis using the bacterial enzyme dextran sucrase from the bacterium Leuconostoc mesenteroides (B512 strain) growing in a sucrose mediumAvailable as dextran-40 & 70 %Mostly used for improving microcirculation

DisadvantagesAnaphylaxisAKICoagulopathyInterference with cross match

GelatinUsed as early as 1915Large molecular weight protein formed by hydrolysis of collagenHas a molecular weight of 5000-50,000

TypesSuccinylated or modified fluid gelatins ( Gelofusine)Urea-cross linked gelatin ( Haemaccel )Oxypolygelatins ( Gelifundol )

IndicationsRegional anesthesiaRenal dysfunctionCP bypass: primingAcute normovolemic hemodilution !!

AdvantagesCan be used liberallyNo effect on renal functionShortest duration of volume expansion

DisadvantagesAnaphylaxisCoagulopathyCirculatory disturbance

STARCH

HeSpan: DuPont Pharmaceuticals ( 1970)First starch product commercially available

Hexastarch: 1st generationPentastarch: 2nd generationTetrastarch: 3rd generation

How are starches described??

ConcentrationMolecular weightMolar substitutionC2-C6 ratio

Concentration3%: hypo-oncotic6%: iso-oncotic10%: hyper-oncotic

Molecular weight( 200/0.5% )POLYDISPERSE SOLUTIONS Weight averaged ( Mw ) Vs number averaged ( Mn )Mw determines viscocityMn indicates oncotic pressureOsmotic effectiveness depends on number of particles not the molecular sizeAvailable in a range from: 70-670 kDa

Molar substitution ( 200/0.5 )Represents average number of hydroxyethyl residues per glucose subunit0.5 MS means : there are 5 hydroxyethyl residues in 10 glucose subunitsHigher the MS, more intravascular retention timeMS determines the category of HES ( heta, hexa, penta, tetra etc )

Starch nomenclature is based on MS

HetastarchHexastarch

TetrastarchPentastarch

C2-C6 ratio { < 8 & > 8 }Not described in product literatureDescribes the pattern of hydroxy-ethylationHydroxy-ethylation of glucose subunits is guided towards C2 & C6 carbon atomsHES products with high C2-C6 ratio undergo slow degradation

TetrastarchLow MWLow MSLow C2-C6 ratioFaster clearanceLess accumulationLesser side effects

TetraHES with similar nomenclature made with different raw materialsBioequivalance between two tetraHES with similar nomenclature made with different raw material might not be same or comparable

Waxy maize Vs Potato starchWaxy maize: 98% highly branched chained amylopectin ( eg. VOLUVEN/ VOLULYTE )Potato starch: heterogenous mixture of 75% amylopectin and remaining with linear chain amylose LOW BRANCHING ( eg. TETRASPAN )

High esterified phosphate group in potato starch HES contributes to more viscosity , due to more branchingClinical significance not clear

Vs?

Safety profile(130/0.4)Less accumulationNegligible effect on coagulationMinimal renal function deteriorationEffective for micro-circulation & tissue oxygenation

Carrier solution

Take home messageKNOW YOUR HESSelect your patient properlyFDA warns use in sepsis and in AKITEST DOSE ( 15-20ml IV, before bolus )Keep a watch on total volume of HES infused