Plasma substitutes

Abstract

Adequate restoration of intravascular volume remains an important therapeutic manoeuvre in managing the surgical, medical and the critically ill intensive care patient. Definition of the ideal volume replacement strategy still remains one of the burning problems. The choice between colloid and crystalloid solutions continues to generate controversy. The highly controversial crystalloid/colloid dispute has been enlarged to a colloid/colloid debate because aside of the natural colloid albumin several non-protein (synthetic) colloids are available as plasma substitutes (e.g. dextrans, gelatins, hydroxyethyl starch [HES] solutions). Due to their varying physico-chemical properties, these solutions widely differ with regard to their pharmacokinetic and pharmacodynamic properties as well as to their hemodynamic efficacy and side-effects. HES is the most intensively studied plasma substitute. The different HES preparations are defined by concentration, molar substitution (MS), mean molecular weight (MW), and the C2/C6 ratio of substitution. Two new HES specification, a third-generation HES with a lower Mw and a lower MS (6% HES 130/0.4) than all other HES preparation and a first-generation HES prepared in a balanced solution, may be promising by improving the therapy of the hypovolemic patient. Albumin cannot be recommended for correction of hypovolemia because of ist extreme costs and because it can easily be replaced by other no-protein colloids. Dextrans should also not be used any more due to the negative effects on coagulation and its high anaphylactic potency. The historical crystalloid/colloid controversy has been focused primarily on outcome. There is increasing evidence that outcome (mortality) is not the correct measure when assessing the ideal volume replacement strategy. New concepts about critical care such as organ perfusion and organ function, the role of inflammation, immunological aspects, and wound healing may change this point of view. Volume replacement has been hitherto often based on art, dogma and personal beliefs. Further well-performed studies in this area will help more to shed new light on the ideal volume replacement strategy of the hypovolemic patient than more meta-analyses that are pooling old-to-very old studies to solve this problem.