Colloids hydroxyethyl starches

Use a crystalloid (normal saline or lactated Ringer s solution) or a colloid (hydroxyethyl starch or albumin 5%) intravenous boluses... 

The colloid hydroxyethyl starch is well tolerated with an incidence of adverse events less than gelatin and dextran. The incidence of allergic reactions is 0.0004 % and the risk of fife-threateiung reactions 0.006-0.085 %. Gelatin, marketed as Haemaccel and Gelofusine , can cause both IgE- and non-IgE-mediated reactions. Clinical manifestations include anaphylaxis, urticaria, bronchospasm, and sneezing. 

Hydroxyethyl starch 5g%(50g/1) Impermeant colloid, suppresses cell swelling... 

Colloids. The overall incidence of reactions has been estimated to less than 0.22%. Gelatins and dextrans are more frequently incriminated than albumin or hetastarch. Evidence for IgE-mediated adverse reactions to gelatin has been reported. Adverse reactions to dextrans were estimated to 0.275%, when it was 0.099% for albumin and 0.058% for hydroxyethyl starch solutions, and 0.03% for gelatin solutions [22, 23]. 

Generally, the major adverse effects associated with colloids are fluid overload, dilutional coagulopathy, and anaphy-lactoid/anaphylactic reactions.24,32 Although derived from pooled human plasma, there is no risk of disease transmission from commercially available albumin or PPF products since they are heated and sterilized by ultrafiltration prior to distribution.24 Because of direct effects on the coagulation system with the hydroxyethyl starch and dextran products, they should be used cautiously in hemorrhagic shock patients. This is another reason why crystalloids maybe preferred in hemorrhagic shock. Furthermore, hetastarch can result in an increase in amylase not associated with pancreatitis. As such, the adverse-effect profiles of the various fluid types should also be considered when selecting a resuscitation fluid. 

Three colloids are currently employed as plasma volume expanders— the two polysaccharides, dextran and hydroxyethyl starch, as well as the polypeptide, gelatin. 

Colloidal isotonic solutions of macromolecules include dextrans (glucose polymer), gelatin (hydrolysed collagen) and hydroxyethyl starch. 

Recent meta-analyses of randomized trials of colloid administration to human critical care patients demonstrated no advantage of colloids over crystalloids and concluded that colloids increased mortality when used in some clinical syndromes (Choi et al 1999, Schierhout Roberts 1998). When trauma patients were studied as a subpopulation, a 12.3% difference in mortality rate was identified in favor of crystalloid therapy. Conversely, analysis of pooled data from nontrauma patients identified a 7.8% difference in mortality rate in favor of colloid treatment (Velanovich 1989). The majority of clinical trials in these meta-analyses compared albumin with crystalloid solutions and thus these results should not discourage the use of hydroxyethyl starches in horses. 

The risks associated with blood transfusions and the shortage of available blood have led to increased administration of substitute solutions for volume expansion. Colloids are commonly used and three of the main colloids commonly administered, gelatin, hydroxyethyl starch, and dextran will be discussed. Each one may cause adverse reactions ranging from grade I with skin manifestations to grade IV involving cardiac and/ or respiratory arrest. 

Etherified starches are synthetic colloids containing over 90% amylopectin, a waxy starch derived from maize, that has been variably etherified. There are two major forms, hetastarch and pentastarch (both BAN and USAN). They are produced synthetically by introducing hydroxyethyl groups into glucose units of starch molecules, followed by acid hydrolysis, which results in a product with a molecular weight of several thousands of daltons. In hetastarch 7 or 8 and in pentastarch 4 or 5 of the hydroxyl groups in each glucose molecule are etherified. 

It should be noted that instead of stabilisation by surfactants the stabilisation of polymer particles may also be achieved by long chain water-soluble polymers. These are usually termed colloids and typical examples are polyvinyl alcohol (Finch, 1973 Finch, 1992), hydroxyethyl cellulose and starch. Stabilisation is again by steric means. The main functions of colloids are ... 

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