Are All Colloids Same? How to Select the Right Colloid?

SUMMARY: The administration of intravenous fluids is one of the most common and universal interventions in medicine. Colloids are an alternative to the frequently used crystalloids, with highly variable use depending on a myriad of clinical variables. A colloid is defined as a high molecular weight (MW) substance that largely remains in the intravascular compartment, thereby generating an oncotic pressure. Colloids are considered to have a greater intravascular persistence when compared to crystalloids. All colloids, however, are clearly not the same. Differences in the physicochemical properties, pharmacokinetics and safety profile exist amongst various colloids. This review explores the different types of colloids, with their properties and usefulness as well as adverse effects. While all the available colloids are reviewed briefly (e.g., albumin, gelatin, dextran) with respect to their pharmacology, indications, advantages and disadvantages, particular emphasis is laid on the hydroxyethyl starches (HES) because of their rising prominence. It is shown that HES differ widely in their physicochemical and pharmacokinetic properties, composition, usefulness, and especially in their adverse effect profiles. The third generation HES (tetrastarches), in particular, seem to offer a unique combination of safety and efficacy. Several issues related to this are discussed in detail. This review of the available clinical data demonstrates that HES should not be regarded as one homogenous group, and data for one product should not be automatically extrapolated to another. Thus, among the synthetic colloids, the tetrastarches appear to offer the best currently available compromise between efficacy, safety profile, and cost. They also appear to be the best suited for use in the intensive care setting. Finally, balanced (rather than saline-based) HES solutions appear promising as a plasma-adapted volume replacement strategy and may further refine the ongoing quest of finding the ideal fluid therapy.