2 Pharmacological characteristics of artificial colloids

Abstract

Water binding colloids (albumin, dextrans, synthetically modified starches and gelatins) which are large enough to remain within the intravascular space play a key role in rational fluid therapy, generating sufficient colloid osmotic pressure gradient against the extra-vascular space to restore and/or maintain normal plasma volume. Apart from their value as plasma volume expanders (10% solutions of dextran or hydroxyethyl starch (HES)) or plasma substitutes (3–6% solutions of albumin, dextran, HES or, to a lesser extent, gelatin), some colloids (dextran and, to a lesser extent, HES) specifically improve microcirculatory perfusion and prevent or attenuate potentially pathological sequelae of cascade activation after surgery, trauma and shock, particularly thromboembolism and ischaemia-reperfusion injury arising from leukocyte-endothelial interaction.

Although all the above colloids are generally well tolerated, high doses of dextran or HES (exceeding 1.5 g/kg) may interfere with haemostasis whilst gelatins may compromise immunodefence (fibronectin opsonizing function). Some protracted storage of persistent residues occurs after HES and rare renal complications have been reported after very high doses of 10% dextran, HES or albumin in dehydrated medical patients. Anaphylactic reactions also occasionally occur with all colloids, particularly after gelatins and dextrans, although hapten inhibition has now virtually eliminated the risk with dextran.