THE CRITICAL NEED FOR COLLOIDS - SELECTING THE RIGHT COLLOID

Part I of this three-part Continuing Education Series discussed fluid dynamics and the distribution of administered fluids in various fluid compartments of the body in health and disease. This part discusses th e characteristics of various natural and synthetic colloids that are a vailable in veterinary medicine. The clinical effects of a colloid dep end largely on its molecular size and its half-life in blood. Colloids with larger numbers of smaller particles (e.g., albumin versus hetast arch) lead to a greater increase in plasma volume. Appropriate selecti on of a colloid regimen depends on the patient's needs (e.g., for red blood cells, albumin, other plasma constituents, or volume expansion). Some colloids have unusual properties that are useful for treating sp ecific cases. For example, dextran 40 coats red blood cells and platel ets and may be helpful in treating patients in hypercoagulable states. Medium-range hydroxyethyl starches might actually plug endothelial ga ps that occur in diseases that lead to the systemic inflammatory respo nse syndrome. Some patients are best managed with a combination of nat ural and synthetic colloids as well as crystalloids. Adverse reactions to colloid therapy include volume overload, transfusion reactions (to blood products), and allergic reactions. Part III of this series will discuss the proper administration of colloids.