Washout kinetics of colloidal starch as a partial or full replacement for plasma exchange

Colloidal starch has been used safely as a plasma expander and an erythrocyte sedimenting agent for over 25 years. However, there remains some concern in regard to the long term sequelae of the administration of large volumes of colloid starch such as would be administered if colloidal starch were used as a plasma replacement during serial plasma exchanges. We identified mathematical relations that allowed for the calculations of the theoretical circulating residual starch in a patient undergoing serial plasma exchanges and used it to model a variety of possible clinical scenarios. Following six one plasma volume exchanges, one would expect only 11, 13, 14, or 17% of the total infused starch to be remaining in the circulation. For example, in the case of a 4L exchange with full replacement, only the starch in 4.1 liters (4L x 6 exchanges x 17% = 4.1L) would be expected to remain in the circulation despite an infusion of 24 L (4L x 6 exchanges = 24L) of starch. The results suggest that relatively small amounts of starch would be expected to remain circulating relative to the large amounts infused following a series of plasma exchanges with partial or full starch replacement.