Hetastarch: an overview of the colloid and its metabolism

Hetastarch, ethoxylated amylopectin, has found clinical utility as a plasma volume expansion agent, a sedimenting agent during pheresis, and a pump priming fluid. Hetastarch is a complex mixture of derivatized amylopectin molecules of various molecular sizes. The derivatization causes resistance to enzymatic hydrolysis, therefore, allowing hetastarch sufficient vascular residence time to be an effective vascular osmotic agent. This has led to its use as a volume expander and to its consequent use as a pump priming fluid. The metabolism of hetastarch proceeds through alpha-amylase hydrolysis of glycosidic bonds, yielding molecules small enough for renal clearance, but does not result in complete hydrolysis. Hence, glucose is not a significant product of hetastarch metabolism. Metabolism proceeds at such a rate that volume expansion is seen for 24-36 hours with a maximum effect (100-172 percent of the infused volume) occurring shortly after infusion. Ninety percent of the dose is eliminated with a half-life of about 17 days.